diff --git a/bazel/testing/lit_test.bzl b/bazel/testing/lit_test.bzl
index cc3c5b973f4e..011eaae6640c 100644
--- a/bazel/testing/lit_test.bzl
+++ b/bazel/testing/lit_test.bzl
@@ -4,7 +4,7 @@
 
 """Rule for a lit test."""
 
-def lit_test(name, test_dir, tools = None, **kwargs):
+def lit_test(name, test_dir, data = None, **kwargs):
     """Runs `lit` on test_dir.
 
     `lit` reference:
@@ -17,22 +17,20 @@ def lit_test(name, test_dir, tools = None, **kwargs):
     Args:
       name: Name of the build rule.
       test_dir: The directory with the lit tests.
-      tools: An optional list of tools to provide to the tests. These will be
+      data: An optional list of tools to provide to the tests. These will be
         aliased for execution.
       **kwargs: Any additional parameters for the generated py_test.
     """
-    if not tools:
-        tools = []
-    tools += [
+    if not data:
+        data = []
+    data += [
         "@llvm-project//llvm:lit",
-        "@llvm-project//llvm:not",
-        "@llvm-project//llvm:FileCheck",
     ]
     native.py_test(
         name = name,
         srcs = ["//bazel/testing:lit_test.py"],
         main = "//bazel/testing:lit_test.py",
-        data = tools + native.glob([test_dir + "/**"]),
-        args = ["--tool=%s" % t for t in tools] + [test_dir, "--"],
+        data = data + native.glob([test_dir + "/**"]),
+        args = [test_dir, "--"],
         **kwargs
     )
diff --git a/bazel/testing/lit_test.py b/bazel/testing/lit_test.py
index 092056db01bc..d22c835b88e2 100644
--- a/bazel/testing/lit_test.py
+++ b/bazel/testing/lit_test.py
@@ -22,9 +22,6 @@ def _parse_args():
     arg_parser.add_argument(
         "lit_args", nargs="*", help="Arguments to pass through to lit."
     )
-    arg_parser.add_argument(
-        "--tool", action="append", help="A tool to add to the PATH."
-    )
     return arg_parser.parse_args()
 
 
@@ -56,29 +53,17 @@ def _normalize(relative_base, target):
 def main():
     parsed_args = _parse_args()
 
-    # A symlink directory is added to the PATH so that commands like `lit` and
-    # `not` can use the versions in the path.
-    symlink_dir = os.environ["TEST_TMPDIR"]
-
-    # Create symlinks to all the tools.
     bin_dir = os.getcwd()
-    relative_base = os.path.dirname(_normalize("", os.environ["TEST_TARGET"]))
-    for tool in parsed_args.tool:
-        tool_path = _normalize(relative_base, tool)
-        symlink_loc = os.path.join(symlink_dir, os.path.basename(tool_path))
-        symlinked_file = os.path.join(bin_dir, tool_path)
-        if not os.path.exists(symlinked_file):
-            raise ValueError("Missing file: %s" % symlinked_file)
-        os.symlink(symlinked_file, symlink_loc)
 
     # Figure out the actual path for the test_dir.
+    relative_base = os.path.dirname(_normalize("", os.environ["TEST_TARGET"]))
     test_dir = os.path.join(
         bin_dir, _normalize(relative_base, parsed_args.test_dir)
     )
 
     args = [
-        os.path.join(symlink_dir, "lit"),
-        "--path=%s" % symlink_dir,
+        os.path.join(os.environ["TEST_SRCDIR"], "llvm-project/llvm/lit"),
+        "--path=%s" % bin_dir,
         test_dir,
         "-sv",
     ]
diff --git a/executable_semantics/BUILD b/executable_semantics/BUILD
index 484026122b6c..b6d7d26921c6 100644
--- a/executable_semantics/BUILD
+++ b/executable_semantics/BUILD
@@ -13,6 +13,7 @@ package(default_visibility = [
 cc_binary(
     name = "executable_semantics",
     srcs = ["main.cpp"],
+    data = ["data/prelude.carbon"],
     deps = [
         "//executable_semantics/common:arena",
         "//executable_semantics/common:nonnull",
@@ -24,8 +25,12 @@ cc_binary(
 
 lit_test(
     name = "executable_semantics_lit_test",
+    data = [
+        ":executable_semantics",
+        "@llvm-project//llvm:FileCheck",
+        "@llvm-project//llvm:not",
+    ],
     test_dir = "testdata",
-    tools = [":executable_semantics"],
 )
 
 py_binary(
diff --git a/executable_semantics/data/prelude.carbon b/executable_semantics/data/prelude.carbon
new file mode 100644
index 000000000000..3244c7d7d5e5
--- /dev/null
+++ b/executable_semantics/data/prelude.carbon
@@ -0,0 +1,11 @@
+// Part of the Carbon Language project, under the Apache License v2.0 with LLVM
+// Exceptions. See /LICENSE for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+package Carbon api;
+
+// Note that Print is experimental, and not part of an accepted proposal, but
+// is included here for printing state in tests.
+fn Print(format_str: String) {
+  __intrinsic_print(format_str);
+}
diff --git a/executable_semantics/main.cpp b/executable_semantics/main.cpp
index 2c750c6609b9..552bd716c84d 100644
--- a/executable_semantics/main.cpp
+++ b/executable_semantics/main.cpp
@@ -2,6 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+#include <unistd.h>
+
 #include <cstdio>
 #include <cstring>
 #include <iostream>
@@ -15,30 +17,15 @@
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/InitLLVM.h"
 
-// The Carbon prelude.
-//
-// TODO: Make this a separate source file that's embedded in the interpreter
-// at build time. See https://github.com/bazelbuild/rules_cc/issues/41 for a
-// possible mechanism.
-static constexpr std::string_view Prelude = R"(
-package Carbon api;
-
-// Note that Print is experimental, and not part of an accepted proposal, but
-// is included here for printing state in tests.
-fn Print(format_str: String) {
-  __intrinsic_print(format_str);
-}
-)";
-
 // Adds the Carbon prelude to `declarations`.
 static void AddPrelude(
-    Carbon::Nonnull<Carbon::Arena*> arena,
+    std::string_view prelude_file_name, Carbon::Nonnull<Carbon::Arena*> arena,
     std::vector<Carbon::Nonnull<Carbon::Declaration*>>* declarations) {
   std::variant<Carbon::AST, Carbon::SyntaxErrorCode> parse_result =
-      ParseFromString(arena, "<prelude>", Prelude, false);
+      Carbon::Parse(arena, prelude_file_name, false);
   if (std::holds_alternative<Carbon::SyntaxErrorCode>(parse_result)) {
     // Try again with tracing, to help diagnose the problem.
-    ParseFromString(arena, "<prelude>", Prelude, true);
+    Carbon::Parse(arena, prelude_file_name, true);
     FATAL() << "Failed to parse prelude.";
   }
   const auto& prelude = std::get<Carbon::AST>(parse_result);
@@ -62,6 +49,9 @@ auto main(int argc, char* argv[]) -> int {
   opt<bool> trace_option("trace", desc("Enable tracing"));
   opt<std::string> input_file_name(llvm::cl::Positional, desc("<input file>"),
                                    llvm::cl::Required);
+  opt<std::string> prelude_file_name(
+      "prelude", desc("<prelude file>"),
+      llvm::cl::init("executable_semantics/data/prelude.carbon"));
 
   llvm::cl::ParseCommandLineOptions(argc, argv);
 
@@ -75,7 +65,7 @@ auto main(int argc, char* argv[]) -> int {
   }
   auto& ast = std::get<Carbon::AST>(ast_or_error);
 
-  AddPrelude(&arena, &ast.declarations);
+  AddPrelude(prelude_file_name, &arena, &ast.declarations);
 
   // Typecheck and run the parsed program.
   Carbon::ExecProgram(&arena, std::get<Carbon::AST>(ast_or_error),
diff --git a/executable_semantics/testdata/assignment_copy/destruct_original.carbon b/executable_semantics/testdata/assignment_copy/destruct_original.carbon
index b363a81164c0..ffc6e9f56844 100644
--- a/executable_semantics/testdata/assignment_copy/destruct_original.carbon
+++ b/executable_semantics/testdata/assignment_copy/destruct_original.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/assignment_copy/reassign_original.carbon b/executable_semantics/testdata/assignment_copy/reassign_original.carbon
index 7df6c5360b5b..1e4052150f5b 100644
--- a/executable_semantics/testdata/assignment_copy/reassign_original.carbon
+++ b/executable_semantics/testdata/assignment_copy/reassign_original.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/basic_syntax/choice.carbon b/executable_semantics/testdata/basic_syntax/choice.carbon
index e3225a9208e9..947eb9456843 100644
--- a/executable_semantics/testdata/basic_syntax/choice.carbon
+++ b/executable_semantics/testdata/basic_syntax/choice.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/basic_syntax/fail_assign_to_function.carbon b/executable_semantics/testdata/basic_syntax/fail_assign_to_function.carbon
index 95cf86a7625a..e818177985d3 100644
--- a/executable_semantics/testdata/basic_syntax/fail_assign_to_function.carbon
+++ b/executable_semantics/testdata/basic_syntax/fail_assign_to_function.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/basic_syntax/fail_assign_to_rval.carbon b/executable_semantics/testdata/basic_syntax/fail_assign_to_rval.carbon
index 681ce0d7ed54..7c5ff87ddbf1 100644
--- a/executable_semantics/testdata/basic_syntax/fail_assign_to_rval.carbon
+++ b/executable_semantics/testdata/basic_syntax/fail_assign_to_rval.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: not executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: not executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{not} %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{not} %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: COMPILATION ERROR: {{.*}}/executable_semantics/testdata/basic_syntax/fail_assign_to_rval.carbon:15: Cannot assign to rvalue '1'
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/basic_syntax/fail_invalid_char.carbon b/executable_semantics/testdata/basic_syntax/fail_invalid_char.carbon
index b9ddd8da473c..1095e19daa2c 100644
--- a/executable_semantics/testdata/basic_syntax/fail_invalid_char.carbon
+++ b/executable_semantics/testdata/basic_syntax/fail_invalid_char.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: not executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: not executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{not} %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{not} %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: COMPILATION ERROR: {{.*}}/executable_semantics/testdata/basic_syntax/fail_invalid_char.carbon:12: invalid character '\xEF' in source file.
 
 �
diff --git a/executable_semantics/testdata/basic_syntax/fail_missing_var.carbon b/executable_semantics/testdata/basic_syntax/fail_missing_var.carbon
index d0e962b83177..529fcdcd831f 100644
--- a/executable_semantics/testdata/basic_syntax/fail_missing_var.carbon
+++ b/executable_semantics/testdata/basic_syntax/fail_missing_var.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: not executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: not executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{not} %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{not} %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: COMPILATION ERROR: {{.*}}/executable_semantics/testdata/basic_syntax/fail_missing_var.carbon:16: syntax error, unexpected COLON
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/basic_syntax/next.carbon b/executable_semantics/testdata/basic_syntax/next.carbon
index 5db9f69cc8fe..53d0584ae114 100644
--- a/executable_semantics/testdata/basic_syntax/next.carbon
+++ b/executable_semantics/testdata/basic_syntax/next.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/basic_syntax/placeholder_variable.carbon b/executable_semantics/testdata/basic_syntax/placeholder_variable.carbon
index 1e514c6b61b2..0014c433e612 100644
--- a/executable_semantics/testdata/basic_syntax/placeholder_variable.carbon
+++ b/executable_semantics/testdata/basic_syntax/placeholder_variable.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/basic_syntax/print.carbon b/executable_semantics/testdata/basic_syntax/print.carbon
index c9fa5ddaec18..8453bf9336e6 100644
--- a/executable_semantics/testdata/basic_syntax/print.carbon
+++ b/executable_semantics/testdata/basic_syntax/print.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: Hello world!
 // CHECK: result: 0
 
diff --git a/executable_semantics/testdata/basic_syntax/record.carbon b/executable_semantics/testdata/basic_syntax/record.carbon
index 5161e4b72892..bb5016b6a1cf 100644
--- a/executable_semantics/testdata/basic_syntax/record.carbon
+++ b/executable_semantics/testdata/basic_syntax/record.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/basic_syntax/star.carbon b/executable_semantics/testdata/basic_syntax/star.carbon
index 10a006d3ecf6..27077412ea31 100644
--- a/executable_semantics/testdata/basic_syntax/star.carbon
+++ b/executable_semantics/testdata/basic_syntax/star.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/basic_syntax/trace.carbon b/executable_semantics/testdata/basic_syntax/trace.carbon
index b73a77787f24..25d2dc001861 100644
--- a/executable_semantics/testdata/basic_syntax/trace.carbon
+++ b/executable_semantics/testdata/basic_syntax/trace.carbon
@@ -2,8 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
 //
 // A lot of output is elided: this is only checking for a few things for simple
 // sanity checking on --trace output.
diff --git a/executable_semantics/testdata/basic_syntax/var_tuple.carbon b/executable_semantics/testdata/basic_syntax/var_tuple.carbon
index cefc8d4a1c84..19d3ab959dd0 100644
--- a/executable_semantics/testdata/basic_syntax/var_tuple.carbon
+++ b/executable_semantics/testdata/basic_syntax/var_tuple.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/basic_syntax/zero.carbon b/executable_semantics/testdata/basic_syntax/zero.carbon
index 985a4039a84c..73945f377051 100644
--- a/executable_semantics/testdata/basic_syntax/zero.carbon
+++ b/executable_semantics/testdata/basic_syntax/zero.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/block/empty.carbon b/executable_semantics/testdata/block/empty.carbon
index 5dfa246821cc..80240f924e8d 100644
--- a/executable_semantics/testdata/block/empty.carbon
+++ b/executable_semantics/testdata/block/empty.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/block/shadowing.carbon b/executable_semantics/testdata/block/shadowing.carbon
index 946652e94ead..d4922f17ecd9 100644
--- a/executable_semantics/testdata/block/shadowing.carbon
+++ b/executable_semantics/testdata/block/shadowing.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/class/assign.carbon b/executable_semantics/testdata/class/assign.carbon
index 17697a144a8a..1648e4d74ed2 100644
--- a/executable_semantics/testdata/class/assign.carbon
+++ b/executable_semantics/testdata/class/assign.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/class/assign_member.carbon b/executable_semantics/testdata/class/assign_member.carbon
index 35dfae04cb88..9560d963704f 100644
--- a/executable_semantics/testdata/class/assign_member.carbon
+++ b/executable_semantics/testdata/class/assign_member.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/class/fail_field_access_mismatch.carbon b/executable_semantics/testdata/class/fail_field_access_mismatch.carbon
index 78084ee04a36..f3defcc54acc 100644
--- a/executable_semantics/testdata/class/fail_field_access_mismatch.carbon
+++ b/executable_semantics/testdata/class/fail_field_access_mismatch.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: not executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: not executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{not} %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{not} %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: COMPILATION ERROR: {{.*}}/executable_semantics/testdata/class/fail_field_access_mismatch.carbon:21: class Point does not have a field named z
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/class/fail_field_mismatch.carbon b/executable_semantics/testdata/class/fail_field_mismatch.carbon
index e0f3eb686c80..b1435c19072a 100644
--- a/executable_semantics/testdata/class/fail_field_mismatch.carbon
+++ b/executable_semantics/testdata/class/fail_field_mismatch.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: not executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: not executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{not} %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{not} %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: COMPILATION ERROR: {{.*}}/executable_semantics/testdata/class/fail_field_mismatch.carbon:20: type error in name binding: '{.x: i32, .z: i32}' is not implicitly convertible to 'class Point'
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/class/fail_field_missing.carbon b/executable_semantics/testdata/class/fail_field_missing.carbon
index d8a880306c89..b591274b7586 100644
--- a/executable_semantics/testdata/class/fail_field_missing.carbon
+++ b/executable_semantics/testdata/class/fail_field_missing.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: not executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: not executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{not} %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{not} %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: COMPILATION ERROR: {{.*}}/executable_semantics/testdata/class/fail_field_missing.carbon:20: type error in name binding: '{.x: i32}' is not implicitly convertible to 'class Point'
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/class/function_param.carbon b/executable_semantics/testdata/class/function_param.carbon
index 982b7240342b..cd22fb4cca1f 100644
--- a/executable_semantics/testdata/class/function_param.carbon
+++ b/executable_semantics/testdata/class/function_param.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/class/global_var.carbon b/executable_semantics/testdata/class/global_var.carbon
index c637a1f4f989..02cb3c7d844e 100644
--- a/executable_semantics/testdata/class/global_var.carbon
+++ b/executable_semantics/testdata/class/global_var.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/class/temp.carbon b/executable_semantics/testdata/class/temp.carbon
index 2cfaac3d9063..527d6ebf6b6c 100644
--- a/executable_semantics/testdata/class/temp.carbon
+++ b/executable_semantics/testdata/class/temp.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/class/var.carbon b/executable_semantics/testdata/class/var.carbon
index e5fa026ed9a3..8875b06b7968 100644
--- a/executable_semantics/testdata/class/var.carbon
+++ b/executable_semantics/testdata/class/var.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/experimental_continuation/await_maintains_scope.carbon b/executable_semantics/testdata/experimental_continuation/await_maintains_scope.carbon
index bff9f8dab9a2..0f461f870e73 100644
--- a/executable_semantics/testdata/experimental_continuation/await_maintains_scope.carbon
+++ b/executable_semantics/testdata/experimental_continuation/await_maintains_scope.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 3
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/experimental_continuation/creation_is_noop.carbon b/executable_semantics/testdata/experimental_continuation/creation_is_noop.carbon
index 3501344ede9b..0f306f91ce3f 100644
--- a/executable_semantics/testdata/experimental_continuation/creation_is_noop.carbon
+++ b/executable_semantics/testdata/experimental_continuation/creation_is_noop.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/experimental_continuation/fail_continuation_syntax.carbon b/executable_semantics/testdata/experimental_continuation/fail_continuation_syntax.carbon
index c1dd75b829f7..68ee4d90df41 100644
--- a/executable_semantics/testdata/experimental_continuation/fail_continuation_syntax.carbon
+++ b/executable_semantics/testdata/experimental_continuation/fail_continuation_syntax.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: not executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: not executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{not} %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{not} %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: COMPILATION ERROR: {{.*}}/executable_semantics/testdata/experimental_continuation/fail_continuation_syntax.carbon:16: syntax error, unexpected identifier, expecting LEFT_CURLY_BRACE
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/experimental_continuation/fail_lifetime.carbon b/executable_semantics/testdata/experimental_continuation/fail_lifetime.carbon
index a1cd95727b79..d3653fcd3b39 100644
--- a/executable_semantics/testdata/experimental_continuation/fail_lifetime.carbon
+++ b/executable_semantics/testdata/experimental_continuation/fail_lifetime.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: not executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: not executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{not} %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{not} %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: RUNTIME ERROR: {{.*}}/executable_semantics/testdata/experimental_continuation/fail_lifetime.carbon:21: undefined behavior: access to dead value 1
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/experimental_continuation/recursive.carbon b/executable_semantics/testdata/experimental_continuation/recursive.carbon
index ebe388d9787e..5211fc6d75a4 100644
--- a/executable_semantics/testdata/experimental_continuation/recursive.carbon
+++ b/executable_semantics/testdata/experimental_continuation/recursive.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 10
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/experimental_continuation/run.carbon b/executable_semantics/testdata/experimental_continuation/run.carbon
index 54503d347961..d5f0e6127a89 100644
--- a/executable_semantics/testdata/experimental_continuation/run.carbon
+++ b/executable_semantics/testdata/experimental_continuation/run.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 1
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/experimental_continuation/run_with_await.carbon b/executable_semantics/testdata/experimental_continuation/run_with_await.carbon
index de710dff0dbd..855ec952e183 100644
--- a/executable_semantics/testdata/experimental_continuation/run_with_await.carbon
+++ b/executable_semantics/testdata/experimental_continuation/run_with_await.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 3
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/experimental_continuation/shallow_copy.carbon b/executable_semantics/testdata/experimental_continuation/shallow_copy.carbon
index c1c70da65ee3..11cac42cfc5d 100644
--- a/executable_semantics/testdata/experimental_continuation/shallow_copy.carbon
+++ b/executable_semantics/testdata/experimental_continuation/shallow_copy.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 3
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/function/auto_return/add.carbon b/executable_semantics/testdata/function/auto_return/add.carbon
index 4c5f322aba4f..3dddebad8c53 100644
--- a/executable_semantics/testdata/function/auto_return/add.carbon
+++ b/executable_semantics/testdata/function/auto_return/add.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/function/auto_return/fail_direct_recurse.carbon b/executable_semantics/testdata/function/auto_return/fail_direct_recurse.carbon
index 1f8086cfd8c6..eff8895f72e8 100644
--- a/executable_semantics/testdata/function/auto_return/fail_direct_recurse.carbon
+++ b/executable_semantics/testdata/function/auto_return/fail_direct_recurse.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: not executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: not executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{not} %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{not} %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: COMPILATION ERROR: {{.*}}/executable_semantics/testdata/function/auto_return/fail_direct_recurse.carbon:18: could not find `Recurse`
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/function/auto_return/fail_multiple_returns.carbon b/executable_semantics/testdata/function/auto_return/fail_multiple_returns.carbon
index 0e249cb9a043..471f15ec1169 100644
--- a/executable_semantics/testdata/function/auto_return/fail_multiple_returns.carbon
+++ b/executable_semantics/testdata/function/auto_return/fail_multiple_returns.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: not executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: not executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{not} %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{not} %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: COMPILATION ERROR: {{.*}}/executable_semantics/testdata/function/auto_return/fail_multiple_returns.carbon:18: Only one return is allowed in a function with an `auto` return type.
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/function/auto_return/fail_no_return.carbon b/executable_semantics/testdata/function/auto_return/fail_no_return.carbon
index 1a610c413fb6..46125efd0374 100644
--- a/executable_semantics/testdata/function/auto_return/fail_no_return.carbon
+++ b/executable_semantics/testdata/function/auto_return/fail_no_return.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: not executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: not executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{not} %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{not} %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: COMPILATION ERROR: {{.*}}/executable_semantics/testdata/function/auto_return/fail_no_return.carbon:15: control-flow reaches end of function that provides a `->` return type without reaching a return statement
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/function/auto_return/fail_separate_decl.carbon b/executable_semantics/testdata/function/auto_return/fail_separate_decl.carbon
index 0e47d3c34ef0..da78bade4ff0 100644
--- a/executable_semantics/testdata/function/auto_return/fail_separate_decl.carbon
+++ b/executable_semantics/testdata/function/auto_return/fail_separate_decl.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: not executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: not executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{not} %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{not} %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: COMPILATION ERROR: {{.*}}/executable_semantics/testdata/function/auto_return/fail_separate_decl.carbon:15: Function declaration has deduced return type but no body
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/function/auto_return/modify_arg_type.carbon b/executable_semantics/testdata/function/auto_return/modify_arg_type.carbon
index e79286fb8e68..373fb258bfab 100644
--- a/executable_semantics/testdata/function/auto_return/modify_arg_type.carbon
+++ b/executable_semantics/testdata/function/auto_return/modify_arg_type.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/function/auto_return/modify_return_type.carbon b/executable_semantics/testdata/function/auto_return/modify_return_type.carbon
index 52aa1fa4df07..7c8b84508da0 100644
--- a/executable_semantics/testdata/function/auto_return/modify_return_type.carbon
+++ b/executable_semantics/testdata/function/auto_return/modify_return_type.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/function/auto_return/type.carbon b/executable_semantics/testdata/function/auto_return/type.carbon
index 4613380d3121..0b33684ee7d3 100644
--- a/executable_semantics/testdata/function/auto_return/type.carbon
+++ b/executable_semantics/testdata/function/auto_return/type.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/function/empty_params.carbon b/executable_semantics/testdata/function/empty_params.carbon
index f24e61a4c7fb..f2d0ab10db72 100644
--- a/executable_semantics/testdata/function/empty_params.carbon
+++ b/executable_semantics/testdata/function/empty_params.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/function/fail_call_with_tuple.carbon b/executable_semantics/testdata/function/fail_call_with_tuple.carbon
index a10df45abf88..d43c1897e342 100644
--- a/executable_semantics/testdata/function/fail_call_with_tuple.carbon
+++ b/executable_semantics/testdata/function/fail_call_with_tuple.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: not executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: not executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{not} %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{not} %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: COMPILATION ERROR: {{.*}}/executable_semantics/testdata/function/fail_call_with_tuple.carbon:19: type error in call: '((i32, i32))' is not implicitly convertible to '(i32, i32)'
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/function/fail_match_no_return.carbon b/executable_semantics/testdata/function/fail_match_no_return.carbon
index ac5a663467fc..6e8f3a038481 100644
--- a/executable_semantics/testdata/function/fail_match_no_return.carbon
+++ b/executable_semantics/testdata/function/fail_match_no_return.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: not executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: not executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{not} %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{not} %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: COMPILATION ERROR: {{.*}}/executable_semantics/testdata/function/fail_match_no_return.carbon:17: control-flow reaches end of function that provides a `->` return type without reaching a return statement
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/function/fail_match_partial_return.carbon b/executable_semantics/testdata/function/fail_match_partial_return.carbon
index 982214a032e3..141214c4d990 100644
--- a/executable_semantics/testdata/function/fail_match_partial_return.carbon
+++ b/executable_semantics/testdata/function/fail_match_partial_return.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: not executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: not executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{not} %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{not} %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: COMPILATION ERROR: {{.*}}/executable_semantics/testdata/function/fail_match_partial_return.carbon:17: control-flow reaches end of function that provides a `->` return type without reaching a return statement
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/function/fail_non_exhaustive_match.carbon b/executable_semantics/testdata/function/fail_non_exhaustive_match.carbon
index 3d513ad52df0..93bb8eb8042c 100644
--- a/executable_semantics/testdata/function/fail_non_exhaustive_match.carbon
+++ b/executable_semantics/testdata/function/fail_non_exhaustive_match.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: not executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: not executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{not} %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{not} %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: COMPILATION ERROR: {{.*}}/executable_semantics/testdata/function/fail_non_exhaustive_match.carbon:18: non-exhaustive match may allow control-flow to reach the end of a function that provides a `->` return type
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/function/fnty.carbon b/executable_semantics/testdata/function/fnty.carbon
index 5c23d590499c..1b301d32286e 100644
--- a/executable_semantics/testdata/function/fnty.carbon
+++ b/executable_semantics/testdata/function/fnty.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/function/ignored_parameter.carbon b/executable_semantics/testdata/function/ignored_parameter.carbon
index 10e1556594f4..04884bba215c 100644
--- a/executable_semantics/testdata/function/ignored_parameter.carbon
+++ b/executable_semantics/testdata/function/ignored_parameter.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/function/multiple_args.carbon b/executable_semantics/testdata/function/multiple_args.carbon
index 5e53db1d6c2a..bc35e2c56396 100644
--- a/executable_semantics/testdata/function/multiple_args.carbon
+++ b/executable_semantics/testdata/function/multiple_args.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/function/param_lifetime.carbon b/executable_semantics/testdata/function/param_lifetime.carbon
index 3e6c733f6ecb..80064f1d2eff 100644
--- a/executable_semantics/testdata/function/param_lifetime.carbon
+++ b/executable_semantics/testdata/function/param_lifetime.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/function/recursive.carbon b/executable_semantics/testdata/function/recursive.carbon
index e9bb80b7818f..292239894101 100644
--- a/executable_semantics/testdata/function/recursive.carbon
+++ b/executable_semantics/testdata/function/recursive.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/function/return.carbon b/executable_semantics/testdata/function/return.carbon
index c3e54f416969..53a3ef74511d 100644
--- a/executable_semantics/testdata/function/return.carbon
+++ b/executable_semantics/testdata/function/return.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/function/return_exhaustive_match.carbon b/executable_semantics/testdata/function/return_exhaustive_match.carbon
index c7dbad4f8aaf..2bab8912d75a 100644
--- a/executable_semantics/testdata/function/return_exhaustive_match.carbon
+++ b/executable_semantics/testdata/function/return_exhaustive_match.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 1
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/function/type_match.carbon b/executable_semantics/testdata/function/type_match.carbon
index 24ad4fd00480..a86c8307df35 100644
--- a/executable_semantics/testdata/function/type_match.carbon
+++ b/executable_semantics/testdata/function/type_match.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/generic_function/apply.carbon b/executable_semantics/testdata/generic_function/apply.carbon
index 83093c624ea1..188519a3915b 100644
--- a/executable_semantics/testdata/generic_function/apply.carbon
+++ b/executable_semantics/testdata/generic_function/apply.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: -2
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/generic_function/fail_not_addable.carbon b/executable_semantics/testdata/generic_function/fail_not_addable.carbon
index 7eb679a2f7e8..1b8755a4aae2 100644
--- a/executable_semantics/testdata/generic_function/fail_not_addable.carbon
+++ b/executable_semantics/testdata/generic_function/fail_not_addable.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: not executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: not executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{not} %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{not} %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: COMPILATION ERROR: {{.*}}/executable_semantics/testdata/generic_function/fail_not_addable.carbon:17: type error in addition(1)
 // CHECK: expected: i32
 // CHECK: actual: T
diff --git a/executable_semantics/testdata/generic_function/fail_type_deduction_mismatch.carbon b/executable_semantics/testdata/generic_function/fail_type_deduction_mismatch.carbon
index b10ea0c05fac..f68befd11b80 100644
--- a/executable_semantics/testdata/generic_function/fail_type_deduction_mismatch.carbon
+++ b/executable_semantics/testdata/generic_function/fail_type_deduction_mismatch.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: not executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: not executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{not} %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{not} %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: COMPILATION ERROR: {{.*}}/executable_semantics/testdata/generic_function/fail_type_deduction_mismatch.carbon:21: type error in argument deduction
 // CHECK: expected: i32
 // CHECK: actual: Bool
diff --git a/executable_semantics/testdata/generic_function/fail_type_deduction_unused.carbon b/executable_semantics/testdata/generic_function/fail_type_deduction_unused.carbon
index a173d12ec209..15e13c03954c 100644
--- a/executable_semantics/testdata/generic_function/fail_type_deduction_unused.carbon
+++ b/executable_semantics/testdata/generic_function/fail_type_deduction_unused.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: not executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: not executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{not} %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{not} %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: COMPILATION ERROR: {{.*}}/executable_semantics/testdata/generic_function/fail_type_deduction_unused.carbon:19: could not deduce type argument for type parameter T
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/generic_function/non_generic_param.carbon b/executable_semantics/testdata/generic_function/non_generic_param.carbon
index 7de0926348f1..7243b4749ae1 100644
--- a/executable_semantics/testdata/generic_function/non_generic_param.carbon
+++ b/executable_semantics/testdata/generic_function/non_generic_param.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 1
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/generic_function/return_val.carbon b/executable_semantics/testdata/generic_function/return_val.carbon
index 5aaa4ffbe7cc..3a17c93aa94f 100644
--- a/executable_semantics/testdata/generic_function/return_val.carbon
+++ b/executable_semantics/testdata/generic_function/return_val.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/generic_function/swap.carbon b/executable_semantics/testdata/generic_function/swap.carbon
index 22072c439b59..68f69d28a035 100644
--- a/executable_semantics/testdata/generic_function/swap.carbon
+++ b/executable_semantics/testdata/generic_function/swap.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/generic_function/tuple_map.carbon b/executable_semantics/testdata/generic_function/tuple_map.carbon
index 604aa984e5ac..ffde6fce722b 100644
--- a/executable_semantics/testdata/generic_function/tuple_map.carbon
+++ b/executable_semantics/testdata/generic_function/tuple_map.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 1
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/generic_function/type_matching.carbon b/executable_semantics/testdata/generic_function/type_matching.carbon
index 08efe36bb81c..b7a39607d355 100644
--- a/executable_semantics/testdata/generic_function/type_matching.carbon
+++ b/executable_semantics/testdata/generic_function/type_matching.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/global_variable/fail_init_order.carbon b/executable_semantics/testdata/global_variable/fail_init_order.carbon
index 11d25f51b4c8..4ddb24c822bd 100644
--- a/executable_semantics/testdata/global_variable/fail_init_order.carbon
+++ b/executable_semantics/testdata/global_variable/fail_init_order.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: not executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: not executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{not} %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{not} %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: RUNTIME ERROR: {{.*}}/executable_semantics/testdata/global_variable/fail_init_order.carbon:17: could not find `y`
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/global_variable/fail_init_type_mismatch.carbon b/executable_semantics/testdata/global_variable/fail_init_type_mismatch.carbon
index 0a95918130a4..8cfd2e4cf536 100644
--- a/executable_semantics/testdata/global_variable/fail_init_type_mismatch.carbon
+++ b/executable_semantics/testdata/global_variable/fail_init_type_mismatch.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: not executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: not executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{not} %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{not} %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: COMPILATION ERROR: {{.*}}/executable_semantics/testdata/global_variable/fail_init_type_mismatch.carbon:16: type error in initializer of variable: 'Bool' is not implicitly convertible to 'i32'
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/global_variable/init_and_read.carbon b/executable_semantics/testdata/global_variable/init_and_read.carbon
index 6bfebd52512f..c3a84a2ac7d4 100644
--- a/executable_semantics/testdata/global_variable/init_and_read.carbon
+++ b/executable_semantics/testdata/global_variable/init_and_read.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/global_variable/init_from_function.carbon b/executable_semantics/testdata/global_variable/init_from_function.carbon
index e6d4e6555624..6226453c1104 100644
--- a/executable_semantics/testdata/global_variable/init_from_function.carbon
+++ b/executable_semantics/testdata/global_variable/init_from_function.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/global_variable/init_order.carbon b/executable_semantics/testdata/global_variable/init_order.carbon
index 8bf873bbc1b5..d682c5157780 100644
--- a/executable_semantics/testdata/global_variable/init_order.carbon
+++ b/executable_semantics/testdata/global_variable/init_order.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/global_variable/shadowing.carbon b/executable_semantics/testdata/global_variable/shadowing.carbon
index e9e1d376e410..112db0fb5764 100644
--- a/executable_semantics/testdata/global_variable/shadowing.carbon
+++ b/executable_semantics/testdata/global_variable/shadowing.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/global_variable/write.carbon b/executable_semantics/testdata/global_variable/write.carbon
index 7498e34a27b6..95559d7e677f 100644
--- a/executable_semantics/testdata/global_variable/write.carbon
+++ b/executable_semantics/testdata/global_variable/write.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/global_variable/write_from_function.carbon b/executable_semantics/testdata/global_variable/write_from_function.carbon
index bd57a017fb4f..a144c891faf0 100644
--- a/executable_semantics/testdata/global_variable/write_from_function.carbon
+++ b/executable_semantics/testdata/global_variable/write_from_function.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/if_else/if_else.carbon b/executable_semantics/testdata/if_else/if_else.carbon
index a0bb44515af9..9cdabcd9b2d8 100644
--- a/executable_semantics/testdata/if_else/if_else.carbon
+++ b/executable_semantics/testdata/if_else/if_else.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/if_else/if_else_if.carbon b/executable_semantics/testdata/if_else/if_else_if.carbon
index 234dcad71629..8886b996a4dd 100644
--- a/executable_semantics/testdata/if_else/if_else_if.carbon
+++ b/executable_semantics/testdata/if_else/if_else_if.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/if_else/if_else_if_else.carbon b/executable_semantics/testdata/if_else/if_else_if_else.carbon
index f2cefba2d261..903a9ca975b0 100644
--- a/executable_semantics/testdata/if_else/if_else_if_else.carbon
+++ b/executable_semantics/testdata/if_else/if_else_if_else.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/if_else/if_false.carbon b/executable_semantics/testdata/if_else/if_false.carbon
index be48637e5bb5..f98fc6d75814 100644
--- a/executable_semantics/testdata/if_else/if_false.carbon
+++ b/executable_semantics/testdata/if_else/if_false.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/if_else/if_nesting.carbon b/executable_semantics/testdata/if_else/if_nesting.carbon
index d2c4e001fe20..628421a899c4 100644
--- a/executable_semantics/testdata/if_else/if_nesting.carbon
+++ b/executable_semantics/testdata/if_else/if_nesting.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/if_else/if_true.carbon b/executable_semantics/testdata/if_else/if_true.carbon
index dc3b41ffff68..c2d05bfcb222 100644
--- a/executable_semantics/testdata/if_else/if_true.carbon
+++ b/executable_semantics/testdata/if_else/if_true.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/import/fail_nonexistent_library.carbon b/executable_semantics/testdata/import/fail_nonexistent_library.carbon
index ecb0a09295fc..51d533532562 100644
--- a/executable_semantics/testdata/import/fail_nonexistent_library.carbon
+++ b/executable_semantics/testdata/import/fail_nonexistent_library.carbon
@@ -4,11 +4,11 @@
 //
 // TODO: This SHOULD fail but doesn't presently.
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/import/fail_nonexistent_package.carbon b/executable_semantics/testdata/import/fail_nonexistent_package.carbon
index c05fe2d031e5..ef10366a7f13 100644
--- a/executable_semantics/testdata/import/fail_nonexistent_package.carbon
+++ b/executable_semantics/testdata/import/fail_nonexistent_package.carbon
@@ -4,11 +4,11 @@
 //
 // TODO: This SHOULD fail but doesn't presently.
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/import/fail_order.carbon b/executable_semantics/testdata/import/fail_order.carbon
index 4a5314e35468..0638963c9fa0 100644
--- a/executable_semantics/testdata/import/fail_order.carbon
+++ b/executable_semantics/testdata/import/fail_order.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: not executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: not executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{not} %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{not} %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: COMPILATION ERROR: {{.*}}/executable_semantics/testdata/import/fail_order.carbon:18: syntax error, unexpected IMPORT, expecting END_OF_FILE
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/lit.cfg b/executable_semantics/testdata/lit.cfg
deleted file mode 100644
index 77b1d1b010b4..000000000000
--- a/executable_semantics/testdata/lit.cfg
+++ /dev/null
@@ -1,9 +0,0 @@
-# Part of the Carbon Language project, under the Apache License v2.0 with LLVM
-# Exceptions. See /LICENSE for license information.
-# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
-
-import lit.formats
-
-config.name = 'lit'
-config.suffixes = ['.carbon']
-config.test_format = lit.formats.ShTest()
diff --git a/executable_semantics/testdata/lit.cfg.py b/executable_semantics/testdata/lit.cfg.py
new file mode 100644
index 000000000000..ad4ba539ab49
--- /dev/null
+++ b/executable_semantics/testdata/lit.cfg.py
@@ -0,0 +1,39 @@
+__copyright__ = """
+Part of the Carbon Language project, under the Apache License v2.0 with LLVM
+Exceptions. See /LICENSE for license information.
+SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+"""
+
+import lit.formats
+import os
+
+
+# This is a provided variable, ignore the undefined name warning.
+config = config  # noqa: F821
+
+
+def fullpath(relative_path):
+    return os.path.join(os.environ["TEST_SRCDIR"], relative_path)
+
+
+config.name = "lit"
+config.suffixes = [".carbon"]
+config.test_format = lit.formats.ShTest()
+
+config.substitutions.append(
+    ("%{prelude}", fullpath("carbon/executable_semantics/data/prelude.carbon"))
+)
+config.substitutions.append(
+    (
+        "%{executable_semantics}",
+        "%s --prelude=%s"
+        % (
+            fullpath("carbon/executable_semantics/executable_semantics"),
+            fullpath("carbon/executable_semantics/data/prelude.carbon"),
+        ),
+    )
+)
+config.substitutions.append(("%{not}", fullpath("llvm-project/llvm/not")))
+config.substitutions.append(
+    ("%{FileCheck}", fullpath("llvm-project/llvm/FileCheck"))
+)
diff --git a/executable_semantics/testdata/match/any_int.carbon b/executable_semantics/testdata/match/any_int.carbon
index 8bb21fe3679f..857d170ecc70 100644
--- a/executable_semantics/testdata/match/any_int.carbon
+++ b/executable_semantics/testdata/match/any_int.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/match/int.carbon b/executable_semantics/testdata/match/int.carbon
index beb6e459fe37..09e6d0b77eba 100644
--- a/executable_semantics/testdata/match/int.carbon
+++ b/executable_semantics/testdata/match/int.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/match/int_default.carbon b/executable_semantics/testdata/match/int_default.carbon
index 94a536dfcfab..a565f228a54d 100644
--- a/executable_semantics/testdata/match/int_default.carbon
+++ b/executable_semantics/testdata/match/int_default.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/match/no_match.carbon b/executable_semantics/testdata/match/no_match.carbon
index 8e9db3a5bf7c..19c3d95ee1af 100644
--- a/executable_semantics/testdata/match/no_match.carbon
+++ b/executable_semantics/testdata/match/no_match.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/match/placeholder.carbon b/executable_semantics/testdata/match/placeholder.carbon
index 9b46bd54b24e..b6e7e5dbd251 100644
--- a/executable_semantics/testdata/match/placeholder.carbon
+++ b/executable_semantics/testdata/match/placeholder.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/name_lookup/fail_block_duplicate.carbon b/executable_semantics/testdata/name_lookup/fail_block_duplicate.carbon
index 91cd29fad2d9..b19082e38e4f 100644
--- a/executable_semantics/testdata/name_lookup/fail_block_duplicate.carbon
+++ b/executable_semantics/testdata/name_lookup/fail_block_duplicate.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: not executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: not executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{not} %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{not} %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: COMPILATION ERROR: {{.*}}/executable_semantics/testdata/name_lookup/fail_block_duplicate.carbon:16: Duplicate name `x` also found at {{.*}}/executable_semantics/testdata/name_lookup/fail_block_duplicate.carbon:15
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/name_lookup/fail_choice_duplicate.carbon b/executable_semantics/testdata/name_lookup/fail_choice_duplicate.carbon
index 81d4627f5a60..1d2cfa79b1d1 100644
--- a/executable_semantics/testdata/name_lookup/fail_choice_duplicate.carbon
+++ b/executable_semantics/testdata/name_lookup/fail_choice_duplicate.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: not executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: not executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{not} %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{not} %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: COMPILATION ERROR: {{.*}}/executable_semantics/testdata/name_lookup/fail_choice_duplicate.carbon:16: Duplicate name `None` in choice type
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/name_lookup/fail_class_duplicate.carbon b/executable_semantics/testdata/name_lookup/fail_class_duplicate.carbon
index d2e992840c7c..00f51814a715 100644
--- a/executable_semantics/testdata/name_lookup/fail_class_duplicate.carbon
+++ b/executable_semantics/testdata/name_lookup/fail_class_duplicate.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: not executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: not executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{not} %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{not} %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: COMPILATION ERROR: {{.*}}/executable_semantics/testdata/name_lookup/fail_class_duplicate.carbon:16: Duplicate name `x` also found at {{.*}}/executable_semantics/testdata/name_lookup/fail_class_duplicate.carbon:15
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/name_lookup/fail_global_duplicate.carbon b/executable_semantics/testdata/name_lookup/fail_global_duplicate.carbon
index 421bbd803ecf..53733a136cc1 100644
--- a/executable_semantics/testdata/name_lookup/fail_global_duplicate.carbon
+++ b/executable_semantics/testdata/name_lookup/fail_global_duplicate.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: not executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: not executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{not} %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{not} %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: COMPILATION ERROR: {{.*}}/executable_semantics/testdata/name_lookup/fail_global_duplicate.carbon:15: Duplicate name `x` also found at {{.*}}/executable_semantics/testdata/name_lookup/fail_global_duplicate.carbon:14
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/name_lookup/fail_match_duplicate.carbon b/executable_semantics/testdata/name_lookup/fail_match_duplicate.carbon
index 94e0790bdbd5..aba335e1f981 100644
--- a/executable_semantics/testdata/name_lookup/fail_match_duplicate.carbon
+++ b/executable_semantics/testdata/name_lookup/fail_match_duplicate.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: not executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: not executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{not} %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{not} %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: COMPILATION ERROR: {{.*}}/executable_semantics/testdata/name_lookup/fail_match_duplicate.carbon:17: Duplicate name `x` also found at {{.*}}/executable_semantics/testdata/name_lookup/fail_match_duplicate.carbon:16
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/name_lookup/fail_use_before_declare.carbon b/executable_semantics/testdata/name_lookup/fail_use_before_declare.carbon
index bc94ed993042..91f2393257a8 100644
--- a/executable_semantics/testdata/name_lookup/fail_use_before_declare.carbon
+++ b/executable_semantics/testdata/name_lookup/fail_use_before_declare.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: not executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: not executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{not} %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{not} %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: COMPILATION ERROR: {{.*}}/executable_semantics/testdata/name_lookup/fail_use_before_declare.carbon:15: could not resolve 'x'
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/name_lookup/global_shadow.carbon b/executable_semantics/testdata/name_lookup/global_shadow.carbon
index 4939b2a2619b..8c0def7b1845 100644
--- a/executable_semantics/testdata/name_lookup/global_shadow.carbon
+++ b/executable_semantics/testdata/name_lookup/global_shadow.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/name_lookup/match_shadow.carbon b/executable_semantics/testdata/name_lookup/match_shadow.carbon
index 0502ae6279d0..ce4f0853fe21 100644
--- a/executable_semantics/testdata/name_lookup/match_shadow.carbon
+++ b/executable_semantics/testdata/name_lookup/match_shadow.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/package/fail_missing.carbon b/executable_semantics/testdata/package/fail_missing.carbon
index af0d0270e302..2018101a5228 100644
--- a/executable_semantics/testdata/package/fail_missing.carbon
+++ b/executable_semantics/testdata/package/fail_missing.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: not executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: not executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{not} %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{not} %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: COMPILATION ERROR: {{.*}}/executable_semantics/testdata/package/fail_missing.carbon:12: syntax error, unexpected FN, expecting PACKAGE
 
 fn Main() -> i32 {
diff --git a/executable_semantics/testdata/package/with_library.carbon b/executable_semantics/testdata/package/with_library.carbon
index 6c347328f143..ff2c2572111c 100644
--- a/executable_semantics/testdata/package/with_library.carbon
+++ b/executable_semantics/testdata/package/with_library.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest library "Foo" api;
diff --git a/executable_semantics/testdata/return/explicit_empty.carbon b/executable_semantics/testdata/return/explicit_empty.carbon
index e439533c7d5b..b389f2394bee 100644
--- a/executable_semantics/testdata/return/explicit_empty.carbon
+++ b/executable_semantics/testdata/return/explicit_empty.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/return/fail_explicit_with_no_return.carbon b/executable_semantics/testdata/return/fail_explicit_with_no_return.carbon
index 94c7e68ba138..be2fbf47fd84 100644
--- a/executable_semantics/testdata/return/fail_explicit_with_no_return.carbon
+++ b/executable_semantics/testdata/return/fail_explicit_with_no_return.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: not executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: not executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{not} %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{not} %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: COMPILATION ERROR: {{.*}}/executable_semantics/testdata/return/fail_explicit_with_no_return.carbon:15: control-flow reaches end of function that provides a `->` return type without reaching a return statement
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/return/fail_explicit_with_plain_return.carbon b/executable_semantics/testdata/return/fail_explicit_with_plain_return.carbon
index ed001bc2c8c2..f857125a1296 100644
--- a/executable_semantics/testdata/return/fail_explicit_with_plain_return.carbon
+++ b/executable_semantics/testdata/return/fail_explicit_with_plain_return.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: not executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: not executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{not} %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{not} %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: COMPILATION ERROR: {{.*}}/executable_semantics/testdata/return/fail_explicit_with_plain_return.carbon:15: return; should provide a return value, to match the function's signature.
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/return/fail_implicit_with_explicit_return.carbon b/executable_semantics/testdata/return/fail_implicit_with_explicit_return.carbon
index c935a15a5fe1..e0b8748b7d71 100644
--- a/executable_semantics/testdata/return/fail_implicit_with_explicit_return.carbon
+++ b/executable_semantics/testdata/return/fail_implicit_with_explicit_return.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: not executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: not executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{not} %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{not} %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: COMPILATION ERROR: {{.*}}/executable_semantics/testdata/return/fail_implicit_with_explicit_return.carbon:15: return (); should not provide a return value, to match the function's signature.
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/return/implicit_with_no_return.carbon b/executable_semantics/testdata/return/implicit_with_no_return.carbon
index 868ca4f9b3d2..e4f0c6971ebf 100644
--- a/executable_semantics/testdata/return/implicit_with_no_return.carbon
+++ b/executable_semantics/testdata/return/implicit_with_no_return.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/return/implicit_with_plain_return.carbon b/executable_semantics/testdata/return/implicit_with_plain_return.carbon
index 616a85bceee1..12b87914eff9 100644
--- a/executable_semantics/testdata/return/implicit_with_plain_return.carbon
+++ b/executable_semantics/testdata/return/implicit_with_plain_return.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/string/basic.carbon b/executable_semantics/testdata/string/basic.carbon
index 2ae72b765ae3..23028652a2c0 100644
--- a/executable_semantics/testdata/string/basic.carbon
+++ b/executable_semantics/testdata/string/basic.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/string/fail_hex_lower.carbon b/executable_semantics/testdata/string/fail_hex_lower.carbon
index 39bab9362d79..145a52b525c8 100644
--- a/executable_semantics/testdata/string/fail_hex_lower.carbon
+++ b/executable_semantics/testdata/string/fail_hex_lower.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: not executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: not executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{not} %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{not} %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: COMPILATION ERROR: {{.*}}/executable_semantics/testdata/string/fail_hex_lower.carbon:15: Invalid escaping in string: "str\xaa"
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/string/fail_hex_truncated.carbon b/executable_semantics/testdata/string/fail_hex_truncated.carbon
index 5d989f476be4..cd8cdb5d510e 100644
--- a/executable_semantics/testdata/string/fail_hex_truncated.carbon
+++ b/executable_semantics/testdata/string/fail_hex_truncated.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: not executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: not executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{not} %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{not} %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: COMPILATION ERROR: {{.*}}/executable_semantics/testdata/string/fail_hex_truncated.carbon:15: Invalid escaping in string: "str\x"
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/string/fail_invalid_escape.carbon b/executable_semantics/testdata/string/fail_invalid_escape.carbon
index e1e923bbdbd9..b6ae4e5bb886 100644
--- a/executable_semantics/testdata/string/fail_invalid_escape.carbon
+++ b/executable_semantics/testdata/string/fail_invalid_escape.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: not executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: not executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{not} %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{not} %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: COMPILATION ERROR: {{.*}}/executable_semantics/testdata/string/fail_invalid_escape.carbon:15: Invalid escaping in string: "str\e"
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/string/fail_newline.carbon b/executable_semantics/testdata/string/fail_newline.carbon
index 9adc787c0376..e700709ceea7 100644
--- a/executable_semantics/testdata/string/fail_newline.carbon
+++ b/executable_semantics/testdata/string/fail_newline.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: not executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: not executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{not} %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{not} %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: COMPILATION ERROR: {{.*}}/executable_semantics/testdata/string/fail_newline.carbon:15: invalid character '\x22' in source file.
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/string/fail_octal.carbon b/executable_semantics/testdata/string/fail_octal.carbon
index 1aa51f70382f..8fb22643be1e 100644
--- a/executable_semantics/testdata/string/fail_octal.carbon
+++ b/executable_semantics/testdata/string/fail_octal.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: not executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: not executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{not} %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{not} %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: COMPILATION ERROR: {{.*}}/executable_semantics/testdata/string/fail_octal.carbon:15: Invalid escaping in string: "str\01"
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/string/fail_tab.carbon b/executable_semantics/testdata/string/fail_tab.carbon
index 1595ffb68cd3..0e446786cd1d 100644
--- a/executable_semantics/testdata/string/fail_tab.carbon
+++ b/executable_semantics/testdata/string/fail_tab.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: not executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: not executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{not} %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{not} %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: COMPILATION ERROR: {{.*}}/executable_semantics/testdata/string/fail_tab.carbon:15: Invalid escaping in string: "new	line"
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/string/hex.carbon b/executable_semantics/testdata/string/hex.carbon
index 2039644d5ba9..36560cdbd944 100644
--- a/executable_semantics/testdata/string/hex.carbon
+++ b/executable_semantics/testdata/string/hex.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/string/newline.carbon b/executable_semantics/testdata/string/newline.carbon
index 84995cd38872..bafd498aee8a 100644
--- a/executable_semantics/testdata/string/newline.carbon
+++ b/executable_semantics/testdata/string/newline.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/struct/assign.carbon b/executable_semantics/testdata/struct/assign.carbon
index a3aae7ceeda5..61730aa97f3a 100644
--- a/executable_semantics/testdata/struct/assign.carbon
+++ b/executable_semantics/testdata/struct/assign.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/struct/assign_member.carbon b/executable_semantics/testdata/struct/assign_member.carbon
index 6c2d153922b8..562e1221f029 100644
--- a/executable_semantics/testdata/struct/assign_member.carbon
+++ b/executable_semantics/testdata/struct/assign_member.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/struct/empty.carbon b/executable_semantics/testdata/struct/empty.carbon
index 60c4307ae957..a75c4911bcca 100644
--- a/executable_semantics/testdata/struct/empty.carbon
+++ b/executable_semantics/testdata/struct/empty.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/struct/ending_comma.carbon b/executable_semantics/testdata/struct/ending_comma.carbon
index 00dd4a5376ae..4d0c0bdde5b1 100644
--- a/executable_semantics/testdata/struct/ending_comma.carbon
+++ b/executable_semantics/testdata/struct/ending_comma.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/struct/equality.carbon b/executable_semantics/testdata/struct/equality.carbon
index fab33c04e751..9f443422fbc3 100644
--- a/executable_semantics/testdata/struct/equality.carbon
+++ b/executable_semantics/testdata/struct/equality.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/struct/equality_false.carbon b/executable_semantics/testdata/struct/equality_false.carbon
index 2925d48a3043..363d87b8c962 100644
--- a/executable_semantics/testdata/struct/equality_false.carbon
+++ b/executable_semantics/testdata/struct/equality_false.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/struct/fail_equality_type.carbon b/executable_semantics/testdata/struct/fail_equality_type.carbon
index c54918c7c7a4..b77e9ffc8333 100644
--- a/executable_semantics/testdata/struct/fail_equality_type.carbon
+++ b/executable_semantics/testdata/struct/fail_equality_type.carbon
@@ -2,8 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: not executable_semantics %s 2>&1 2>&1 | FileCheck %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{not} %{executable_semantics} %s 2>&1 2>&1 | FileCheck %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: COMPILATION ERROR: {{.*}}/executable_semantics/testdata/struct/fail_equality_type.carbon:16: type error in ==
 // CHECK: expected: {.x: i32, .y: i32}
 // CHECK: actual: {.x: i32}
diff --git a/executable_semantics/testdata/struct/fail_field_access_mismatch.carbon b/executable_semantics/testdata/struct/fail_field_access_mismatch.carbon
index 500f495e70b8..a7ee9df973f7 100644
--- a/executable_semantics/testdata/struct/fail_field_access_mismatch.carbon
+++ b/executable_semantics/testdata/struct/fail_field_access_mismatch.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: not executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: not executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{not} %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{not} %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: COMPILATION ERROR: {{.*}}/executable_semantics/testdata/struct/fail_field_access_mismatch.carbon:15: struct {.x: i32, .y: i32} does not have a field named z
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/struct/name_order.carbon b/executable_semantics/testdata/struct/name_order.carbon
index f0c4ca792d58..fce18caa07aa 100644
--- a/executable_semantics/testdata/struct/name_order.carbon
+++ b/executable_semantics/testdata/struct/name_order.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/struct/temp.carbon b/executable_semantics/testdata/struct/temp.carbon
index 5c75308b4032..4edd49d6eb2d 100644
--- a/executable_semantics/testdata/struct/temp.carbon
+++ b/executable_semantics/testdata/struct/temp.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/struct/var.carbon b/executable_semantics/testdata/struct/var.carbon
index cb99794ce34e..02957e92d968 100644
--- a/executable_semantics/testdata/struct/var.carbon
+++ b/executable_semantics/testdata/struct/var.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/tuple/ending_comma.carbon b/executable_semantics/testdata/tuple/ending_comma.carbon
index b8db56402f88..032dfd1afc8d 100644
--- a/executable_semantics/testdata/tuple/ending_comma.carbon
+++ b/executable_semantics/testdata/tuple/ending_comma.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/tuple/equality.carbon b/executable_semantics/testdata/tuple/equality.carbon
index 4418ad3f90ae..b4cc8d4a552d 100644
--- a/executable_semantics/testdata/tuple/equality.carbon
+++ b/executable_semantics/testdata/tuple/equality.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/tuple/equality_false.carbon b/executable_semantics/testdata/tuple/equality_false.carbon
index bfd36ae48ddd..25a6db85ca13 100644
--- a/executable_semantics/testdata/tuple/equality_false.carbon
+++ b/executable_semantics/testdata/tuple/equality_false.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/tuple/fail_equality_type.carbon b/executable_semantics/testdata/tuple/fail_equality_type.carbon
index e25802951178..543055705bc1 100644
--- a/executable_semantics/testdata/tuple/fail_equality_type.carbon
+++ b/executable_semantics/testdata/tuple/fail_equality_type.carbon
@@ -2,8 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: not executable_semantics %s 2>&1 2>&1 | FileCheck %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{not} %{executable_semantics} %s 2>&1 2>&1 | FileCheck %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: COMPILATION ERROR: {{.*}}/executable_semantics/testdata/tuple/fail_equality_type.carbon:16: type error in ==
 // CHECK: expected: (i32, i32)
 // CHECK: actual: (i32)
diff --git a/executable_semantics/testdata/tuple/fail_index.carbon b/executable_semantics/testdata/tuple/fail_index.carbon
index 7c0b8c230ea1..fee2b4f606f7 100644
--- a/executable_semantics/testdata/tuple/fail_index.carbon
+++ b/executable_semantics/testdata/tuple/fail_index.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: not executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: not executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{not} %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{not} %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: COMPILATION ERROR: {{.*}}/executable_semantics/testdata/tuple/fail_index.carbon:16: index 2 is out of range for type (i32, i32)
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/tuple/fail_index_var.carbon b/executable_semantics/testdata/tuple/fail_index_var.carbon
index 83fcc43c5d5d..ee6a01c3242f 100644
--- a/executable_semantics/testdata/tuple/fail_index_var.carbon
+++ b/executable_semantics/testdata/tuple/fail_index_var.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: not executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: not executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{not} %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{not} %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: RUNTIME ERROR: {{.*}}/executable_semantics/testdata/tuple/fail_index_var.carbon:17: could not find `index`
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/tuple/index.carbon b/executable_semantics/testdata/tuple/index.carbon
index 21809bb4a9d5..ef5361ee1245 100644
--- a/executable_semantics/testdata/tuple/index.carbon
+++ b/executable_semantics/testdata/tuple/index.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/tuple/match.carbon b/executable_semantics/testdata/tuple/match.carbon
index 8159fcf51808..05a4bdd24901 100644
--- a/executable_semantics/testdata/tuple/match.carbon
+++ b/executable_semantics/testdata/tuple/match.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/tuple/match_nested.carbon b/executable_semantics/testdata/tuple/match_nested.carbon
index b2bf2b0f981d..482bd394806d 100644
--- a/executable_semantics/testdata/tuple/match_nested.carbon
+++ b/executable_semantics/testdata/tuple/match_nested.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/tuple/no_ending_comma.carbon b/executable_semantics/testdata/tuple/no_ending_comma.carbon
index b977324db3c2..c02b9a76a9aa 100644
--- a/executable_semantics/testdata/tuple/no_ending_comma.carbon
+++ b/executable_semantics/testdata/tuple/no_ending_comma.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/while/basic.carbon b/executable_semantics/testdata/while/basic.carbon
index 5edc6f63a98d..0142173e1ce7 100644
--- a/executable_semantics/testdata/while/basic.carbon
+++ b/executable_semantics/testdata/while/basic.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/while/break.carbon b/executable_semantics/testdata/while/break.carbon
index 5d7aba504b76..764b9e434301 100644
--- a/executable_semantics/testdata/while/break.carbon
+++ b/executable_semantics/testdata/while/break.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/testdata/while/continue.carbon b/executable_semantics/testdata/while/continue.carbon
index aca1256a2c65..dc0f6d83c421 100644
--- a/executable_semantics/testdata/while/continue.carbon
+++ b/executable_semantics/testdata/while/continue.carbon
@@ -2,11 +2,11 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// RUN: executable_semantics %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
-// RUN: executable_semantics --trace %s 2>&1 | \
-// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
-// AUTOUPDATE: executable_semantics %s
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
 // CHECK: result: 0
 
 package ExecutableSemanticsTest api;
diff --git a/executable_semantics/update_checks.py b/executable_semantics/update_checks.py
index 1e6883a96539..f603c28b965c 100755
--- a/executable_semantics/update_checks.py
+++ b/executable_semantics/update_checks.py
@@ -14,7 +14,7 @@ import subprocess
 import sys
 from typing import Set
 
-_BINDIR = "./bazel-bin/executable_semantics"
+_BIN = "./bazel-bin/executable_semantics/executable_semantics"
 _TESTDATA = "executable_semantics/testdata"
 
 # A prefix followed by a command to run for autoupdating checked output.
@@ -29,7 +29,7 @@ def _get_tests() -> Set[str]:
     tests = set()
     for root, _, files in os.walk(_TESTDATA):
         for f in files:
-            if f == "lit.cfg":
+            if f == "lit.cfg.py":
                 # Ignore the lit config.
                 continue
             if os.path.splitext(f)[1] == ".carbon":
@@ -74,9 +74,8 @@ def _update_check_once(test: str) -> bool:
             % (test, _AUTOUPDATE_MARKER, _NOAUTOUPDATE_MARKER)
         )
 
-    # Add executable_semantics to the PATH.
-    env = os.environ.copy()
-    env["PATH"] = "%s:%s" % (os.path.abspath(_BINDIR), env["PATH"])
+    # Mirror lit.cfg.py substitutions; bazel runs don't need --prelude.
+    autoupdate_cmd = autoupdate_cmd.replace("%{executable_semantics}", _BIN)
 
     # Run the autoupdate command to generate output.
     # (`bazel run` would serialize)
@@ -85,7 +84,6 @@ def _update_check_once(test: str) -> bool:
         shell=True,
         stdout=subprocess.PIPE,
         stderr=subprocess.STDOUT,
-        env=env,
     )
     out = p.stdout.decode("utf-8")