diff --git a/testing/file_test/README.md b/testing/file_test/README.md
index ca9513cde650..7f39679c7959 100644
--- a/testing/file_test/README.md
+++ b/testing/file_test/README.md
@@ -80,6 +80,21 @@ The main test file and any split-files must have a `fail_` prefix if and only if
 they have an associated error. An exception is that the main test file may omit
 `fail_` when it contains split-files that have a `fail_` prefix.
 
+## Content replacement
+
+Some keywords can be inserted for content:
+
+-   ```
+    [[@TEST_NAME]]
+    ```
+
+    Replaces with the test name, which is the filename with the extension and
+    any `fail_` or `todo_` prefixes removed. For split files, this is based on
+    the split filename.
+
+The `[[@` string is reserved for future replacements, but `[[` is allowed in
+content (comment markers don't allow `[[`).
+
 ## Comment markers
 
 Settings in files are provided in comments, similar to `FileCheck` syntax.
@@ -106,7 +121,9 @@ Supported comment markers are:
     check line refers to any line in the test, all STDOUT check lines are placed
     at the end of the file instead of immediately after AUTOUPDATE.
 
--   `// ARGS: <arguments>`
+-   ```
+    // ARGS: <arguments>
+    ```
 
     Provides a space-separated list of arguments, which will be passed to
     RunWithFiles as test_args. These are intended for use by the command as
@@ -131,7 +148,9 @@ Supported comment markers are:
     ARGS can be specified at most once. If not provided, the FileTestBase child
     is responsible for providing default arguments.
 
--   `// SET-CHECK-SUBSET`
+-   ```
+    // SET-CHECK-SUBSET
+    ```
 
     By default, all lines of output must have a CHECK match. Adding this as a
     option sets it so that non-matching lines are ignored. All provided
@@ -139,7 +158,9 @@ Supported comment markers are:
 
     SET-CHECK-SUBSET can be specified at most once.
 
--   `// --- <filename>`
+-   ```
+    // --- <filename>
+    ```
 
     By default, all file content is provided to the test as a single file in
     test_files. Using this marker allows the file to be split into multiple
diff --git a/testing/file_test/file_test_base.cpp b/testing/file_test/file_test_base.cpp
index 32627c6964c2..d6777b483e7b 100644
--- a/testing/file_test/file_test_base.cpp
+++ b/testing/file_test/file_test_base.cpp
@@ -443,7 +443,7 @@ struct SplitState {
   auto has_splits() const -> bool { return file_index > 0; }
 
   auto add_content(llvm::StringRef line) -> void {
-    content.append(line);
+    content.append(line.str());
     content.append("\n");
   }
 
@@ -462,13 +462,63 @@ struct SplitState {
   int file_index = 0;
 };
 
+// Replaces the content keywords.
+//
+// TEST_NAME is the only content keyword at present, but we do validate that
+// other names are reserved.
+static auto ReplaceContentKeywords(llvm::StringRef filename,
+                                   std::string* content) -> ErrorOr<Success> {
+  static constexpr llvm::StringLiteral Prefix = "[[@";
+
+  auto keyword_pos = content->find(Prefix);
+  // Return early if not finding anything.
+  if (keyword_pos == std::string::npos) {
+    return Success();
+  }
+
+  // Construct the test name by getting the base name without the extension,
+  // then removing any "fail_" or "todo_" prefixes.
+  llvm::StringRef test_name = filename;
+  if (auto last_slash = test_name.rfind("/");
+      last_slash != llvm::StringRef::npos) {
+    test_name = test_name.substr(last_slash + 1);
+  }
+  if (auto ext_dot = test_name.find("."); ext_dot != llvm::StringRef::npos) {
+    test_name = test_name.substr(0, ext_dot);
+  }
+  // Note this also handles `fail_todo_` and `todo_fail_`.
+  test_name.consume_front("todo_");
+  test_name.consume_front("fail_");
+  test_name.consume_front("todo_");
+
+  while (keyword_pos != std::string::npos) {
+    static constexpr llvm::StringLiteral TestName = "[[@TEST_NAME]]";
+    auto keyword = llvm::StringRef(*content).substr(keyword_pos);
+    if (keyword.starts_with(TestName)) {
+      content->replace(keyword_pos, TestName.size(), test_name);
+      keyword_pos += test_name.size();
+    } else if (keyword.starts_with("[[@LINE")) {
+      // Just move past the prefix to find the next one.
+      keyword_pos += Prefix.size();
+    } else {
+      return ErrorBuilder()
+             << "Unexpected use of `[[@` at `" << keyword.substr(0, 5) << "`";
+    }
+    keyword_pos = content->find(Prefix, keyword_pos);
+  }
+  return Success();
+}
+
 // Adds a file. Used for both split and unsplit test files.
 static auto AddTestFile(llvm::StringRef filename, std::string* content,
                         llvm::SmallVector<FileTestBase::TestFile>* test_files)
-    -> void {
+    -> ErrorOr<Success> {
+  CARBON_RETURN_IF_ERROR(ReplaceContentKeywords(filename, content));
+
   test_files->push_back(
       {.filename = filename.str(), .content = std::move(*content)});
   content->clear();
+  return Success();
 }
 
 // Process file split ("---") lines when found. Returns true if the line is
@@ -500,7 +550,8 @@ static auto TryConsumeSplit(
 
   // On a file split, add the previous file, then start a new one.
   if (split->has_splits()) {
-    AddTestFile(split->filename, &split->content, test_files);
+    CARBON_RETURN_IF_ERROR(
+        AddTestFile(split->filename, &split->content, test_files));
   } else {
     split->content.clear();
     if (split->found_code_pre_split) {
@@ -646,14 +697,14 @@ static auto TransformExpectation(int line_index, llvm::StringRef in)
 // Once all content is processed, do any remaining split processing.
 static auto FinishSplit(llvm::StringRef test_name, SplitState* split,
                         llvm::SmallVector<FileTestBase::TestFile>* test_files)
-    -> void {
+    -> ErrorOr<Success> {
   if (split->has_splits()) {
-    AddTestFile(split->filename, &split->content, test_files);
+    return AddTestFile(split->filename, &split->content, test_files);
   } else {
     // If no file splitting happened, use the main file as the test file.
     // There will always be a `/` unless tests are in the repo root.
-    AddTestFile(test_name.drop_front(test_name.rfind("/") + 1), &split->content,
-                test_files);
+    return AddTestFile(test_name.drop_front(test_name.rfind("/") + 1),
+                       &split->content, test_files);
   }
 }
 
@@ -826,7 +877,7 @@ auto FileTestBase::ProcessTestFile(TestContext& context) -> ErrorOr<Success> {
   }
 
   context.has_splits = split.has_splits();
-  FinishSplit(test_name_, &split, &context.test_files);
+  CARBON_RETURN_IF_ERROR(FinishSplit(test_name_, &split, &context.test_files));
 
   // Assume there is always a suffix `\n` in output.
   if (!context.expected_stdout.empty()) {
diff --git a/testing/file_test/file_test_base_test.cpp b/testing/file_test/file_test_base_test.cpp
index 3934b1e1a1dc..3e4ef6887934 100644
--- a/testing/file_test/file_test_base_test.cpp
+++ b/testing/file_test/file_test_base_test.cpp
@@ -9,6 +9,7 @@
 
 #include "common/ostream.h"
 #include "llvm/ADT/StringExtras.h"
+#include "llvm/ADT/StringSwitch.h"
 #include "llvm/Support/FormatVariadic.h"
 
 namespace Carbon::Testing {
@@ -21,121 +22,8 @@ class FileTestBaseTest : public FileTestBase {
 
   auto Run(const llvm::SmallVector<llvm::StringRef>& test_args,
            llvm::vfs::InMemoryFileSystem& fs, llvm::raw_pwrite_stream& stdout,
-           llvm::raw_pwrite_stream& stderr) -> ErrorOr<RunResult> override {
-    llvm::ArrayRef<llvm::StringRef> args = test_args;
+           llvm::raw_pwrite_stream& stderr) -> ErrorOr<RunResult> override;
 
-    llvm::ListSeparator sep;
-    stdout << args.size() << " args: ";
-    for (auto arg : args) {
-      stdout << sep << "`" << arg << "`";
-    }
-    stdout << "\n";
-
-    auto filename = std::filesystem::path(test_name().str()).filename();
-    if (filename == "args.carbon") {
-      // 'args.carbon' has custom arguments, so don't do regular argument
-      // validation for it.
-      return {{.success = true}};
-    }
-
-    if (args.empty() || args.front() != "default_args") {
-      return ErrorBuilder() << "missing `default_args` argument";
-    }
-    args = args.drop_front();
-
-    for (auto arg : args) {
-      if (!fs.exists(arg)) {
-        return ErrorBuilder() << "Missing file: " << arg;
-      }
-    }
-
-    if (filename == "example.carbon") {
-      int delta_line = 10;
-      stdout << "something\n"
-             << "\n"
-             << "example.carbon:" << delta_line + 1 << ": Line delta\n"
-             << "example.carbon:" << delta_line << ": Negative line delta\n"
-             << "+*[]{}\n"
-             << "Foo baz\n";
-      return {{.success = true}};
-    } else if (filename == "fail_example.carbon") {
-      stderr << "Oops\n";
-      return {{.success = false}};
-    } else if (filename == "two_files.carbon" ||
-               filename == "not_split.carbon") {
-      for (auto arg : args) {
-        // Describe file contents to stdout to validate splitting.
-        auto file = fs.getBufferForFile(arg, /*FileSize=*/-1,
-                                        /*RequiresNullTerminator=*/false);
-        if (file.getError()) {
-          return Error(file.getError().message());
-        }
-        llvm::StringRef content = file.get()->getBuffer();
-        stdout << arg << ":1: starts with \"";
-        stdout.write_escaped(content.take_front(40));
-        stdout << "\", length " << content.count('\n') << " lines\n";
-      }
-      return {{.success = true}};
-    } else if (filename == "alternating_files.carbon") {
-      stdout << "unattached message 1\n"
-             << "a.carbon:2: message 2\n"
-             << "b.carbon:5: message 3\n"
-             << "a.carbon:2: message 4\n"
-             << "b.carbon:5: message 5\n"
-             << "unattached message 6\n";
-      stderr << "unattached message 1\n"
-             << "a.carbon:2: message 2\n"
-             << "b.carbon:5: message 3\n"
-             << "a.carbon:2: message 4\n"
-             << "b.carbon:5: message 5\n"
-             << "unattached message 6\n";
-      return {{.success = true}};
-    } else if (filename == "unattached_multi_file.carbon") {
-      stdout << "unattached message 1\n"
-             << "unattached message 2\n";
-      stderr << "unattached message 3\n"
-             << "unattached message 4\n";
-      return {{.success = true}};
-    } else if (filename == "file_only_re_one_file.carbon") {
-      stdout << "unattached message 1\n"
-             << "file: file_only_re_one_file.carbon\n"
-             << "line: 1\n"
-             << "unattached message 2\n";
-      return {{.success = true}};
-    } else if (filename == "file_only_re_multi_file.carbon") {
-      int msg_count = 0;
-      stdout << "unattached message " << ++msg_count << "\n"
-             << "file: a.carbon\n"
-             << "unattached message " << ++msg_count << "\n"
-             << "line: 3: attached message " << ++msg_count << "\n"
-             << "unattached message " << ++msg_count << "\n"
-             << "line: 8: late message " << ++msg_count << "\n"
-             << "unattached message " << ++msg_count << "\n"
-             << "file: b.carbon\n"
-             << "line: 2: attached message " << ++msg_count << "\n"
-             << "unattached message " << ++msg_count << "\n"
-             << "line: 7: late message " << ++msg_count << "\n"
-             << "unattached message " << ++msg_count << "\n";
-      return {{.success = true}};
-    } else if (filename == "fail_multi_success_overall_fail.carbon") {
-      RunResult result = {.success = false};
-      result.per_file_success.push_back({"a.carbon", true});
-      result.per_file_success.push_back({"b.carbon", true});
-      return result;
-    } else if (filename == "multi_success.carbon") {
-      RunResult result = {.success = true};
-      result.per_file_success.push_back({"a.carbon", true});
-      result.per_file_success.push_back({"b.carbon", true});
-      return result;
-    } else if (filename == "multi_success_and_fail.carbon") {
-      RunResult result = {.success = false};
-      result.per_file_success.push_back({"a.carbon", true});
-      result.per_file_success.push_back({"fail_b.carbon", false});
-      return result;
-    } else {
-      return ErrorBuilder() << "Unexpected file: " << filename;
-    }
-  }
   auto GetArgReplacements() -> llvm::StringMap<std::string> override {
     return {{"replacement", "replaced"}};
   }
@@ -163,6 +51,208 @@ class FileTestBaseTest : public FileTestBase {
   }
 };
 
+// Prints arguments so that they can be validated in tests.
+static auto PrintArgs(llvm::ArrayRef<llvm::StringRef> args,
+                      llvm::raw_pwrite_stream& stdout) -> void {
+  llvm::ListSeparator sep;
+  stdout << args.size() << " args: ";
+  for (auto arg : args) {
+    stdout << sep << "`" << arg << "`";
+  }
+  stdout << "\n";
+}
+
+// Verifies arguments are well-structured, and returns the files in them.
+static auto GetFilesFromArgs(llvm::ArrayRef<llvm::StringRef> args,
+                             llvm::vfs::InMemoryFileSystem& fs)
+    -> ErrorOr<llvm::ArrayRef<llvm::StringRef>> {
+  if (args.empty() || args.front() != "default_args") {
+    return ErrorBuilder() << "missing `default_args` argument";
+  }
+  args = args.drop_front();
+
+  for (auto arg : args) {
+    if (!fs.exists(arg)) {
+      return ErrorBuilder() << "Missing file: " << arg;
+    }
+  }
+  return args;
+}
+
+// Parameters used to by individual test handlers, for easy value forwarding.
+struct TestParams {
+  // These are the arguments to `Run()`.
+  llvm::vfs::InMemoryFileSystem& fs;
+  llvm::raw_pwrite_stream& stdout;
+  llvm::raw_pwrite_stream& stderr;
+
+  // This is assigned after construction.
+  llvm::ArrayRef<llvm::StringRef> files;
+};
+
+// Does printing and returns expected results for alternating_files.carbon.
+static auto TestAlternatingFiles(TestParams& params)
+    -> ErrorOr<FileTestBaseTest::RunResult> {
+  params.stdout << "unattached message 1\n"
+                << "a.carbon:2: message 2\n"
+                << "b.carbon:5: message 3\n"
+                << "a.carbon:2: message 4\n"
+                << "b.carbon:5: message 5\n"
+                << "unattached message 6\n";
+  params.stderr << "unattached message 1\n"
+                << "a.carbon:2: message 2\n"
+                << "b.carbon:5: message 3\n"
+                << "a.carbon:2: message 4\n"
+                << "b.carbon:5: message 5\n"
+                << "unattached message 6\n";
+  return {{.success = true}};
+}
+
+// Does printing and returns expected results for example.carbon.
+static auto TestExample(TestParams& params)
+    -> ErrorOr<FileTestBaseTest::RunResult> {
+  int delta_line = 10;
+  params.stdout << "something\n"
+                << "\n"
+                << "example.carbon:" << delta_line + 1 << ": Line delta\n"
+                << "example.carbon:" << delta_line << ": Negative line delta\n"
+                << "+*[]{}\n"
+                << "Foo baz\n";
+  return {{.success = true}};
+}
+
+// Does printing and returns expected results for fail_example.carbon.
+static auto TestFailExample(TestParams& params)
+    -> ErrorOr<FileTestBaseTest::RunResult> {
+  params.stderr << "Oops\n";
+  return {{.success = false}};
+}
+
+// Does printing and returns expected results for
+// file_only_re_multi_file.carbon.
+static auto TestFileOnlyREMultiFile(TestParams& params)
+    -> ErrorOr<FileTestBaseTest::RunResult> {
+  int msg_count = 0;
+  params.stdout << "unattached message " << ++msg_count << "\n"
+                << "file: a.carbon\n"
+                << "unattached message " << ++msg_count << "\n"
+                << "line: 3: attached message " << ++msg_count << "\n"
+                << "unattached message " << ++msg_count << "\n"
+                << "line: 8: late message " << ++msg_count << "\n"
+                << "unattached message " << ++msg_count << "\n"
+                << "file: b.carbon\n"
+                << "line: 2: attached message " << ++msg_count << "\n"
+                << "unattached message " << ++msg_count << "\n"
+                << "line: 7: late message " << ++msg_count << "\n"
+                << "unattached message " << ++msg_count << "\n";
+  return {{.success = true}};
+}
+
+// Does printing and returns expected results for file_only_re_one_file.carbon.
+static auto TestFileOnlyREOneFile(TestParams& params)
+    -> ErrorOr<FileTestBaseTest::RunResult> {
+  params.stdout << "unattached message 1\n"
+                << "file: file_only_re_one_file.carbon\n"
+                << "line: 1\n"
+                << "unattached message 2\n";
+  return {{.success = true}};
+}
+
+// Does printing and returns expected results for unattached_multi_file.carbon.
+static auto TestUnattachedMultiFile(TestParams& params)
+    -> ErrorOr<FileTestBaseTest::RunResult> {
+  params.stdout << "unattached message 1\n"
+                << "unattached message 2\n";
+  params.stderr << "unattached message 3\n"
+                << "unattached message 4\n";
+  return {{.success = true}};
+}
+
+// Does printing and returns expected results for:
+// - fail_multi_success_overall_fail.carbon
+// - multi_success.carbon
+// - multi_success_and_fail.carbon
+//
+// Parameters indicate overall and per-file success.
+static auto HandleMultiSuccessTests(bool overall, bool a, bool b)
+    -> ErrorOr<FileTestBaseTest::RunResult> {
+  FileTestBaseTest::RunResult result = {.success = overall};
+  result.per_file_success.push_back({a ? "a.carbon" : "fail_a.carbon", a});
+  result.per_file_success.push_back({b ? "b.carbon" : "fail_b.carbon", b});
+  return result;
+}
+
+// Echoes back non-comment file content. Used for default file handling.
+static auto EchoFileContent(TestParams& params)
+    -> ErrorOr<FileTestBaseTest::RunResult> {
+  // By default, echo non-comment content of files back.
+  for (auto test_file : params.files) {
+    // Describe file contents to stdout to validate splitting.
+    auto file = params.fs.getBufferForFile(test_file, /*FileSize=*/-1,
+                                           /*RequiresNullTerminator=*/false);
+    if (file.getError()) {
+      return Error(file.getError().message());
+    }
+    llvm::StringRef buffer = file.get()->getBuffer();
+    for (int line_number = 1; !buffer.empty(); ++line_number) {
+      auto [line, remainder] = buffer.split('\n');
+      if (!line.empty() && !line.starts_with("//")) {
+        params.stdout << test_file << ":" << line_number << ": " << line
+                      << "\n";
+      }
+      buffer = remainder;
+    }
+  }
+  return {{.success = true}};
+}
+
+auto FileTestBaseTest::Run(const llvm::SmallVector<llvm::StringRef>& test_args,
+                           llvm::vfs::InMemoryFileSystem& fs,
+                           llvm::raw_pwrite_stream& stdout,
+                           llvm::raw_pwrite_stream& stderr)
+    -> ErrorOr<RunResult> {
+  PrintArgs(test_args, stdout);
+
+  auto filename = std::filesystem::path(test_name().str()).filename();
+  if (filename == "args.carbon") {
+    // 'args.carbon' has custom arguments, so don't do regular argument
+    // validation for it.
+    return {{.success = true}};
+  }
+
+  // Choose the test function based on filename.
+  auto test_fn =
+      llvm::StringSwitch<std::function<ErrorOr<RunResult>(TestParams&)>>(
+          filename.string())
+          .Case("alternating_files.carbon", &TestAlternatingFiles)
+          .Case("example.carbon", &TestExample)
+          .Case("fail_example.carbon", &TestFailExample)
+          .Case("file_only_re_one_file.carbon", &TestFileOnlyREOneFile)
+          .Case("file_only_re_multi_file.carbon", &TestFileOnlyREMultiFile)
+          .Case("unattached_multi_file.carbon", &TestUnattachedMultiFile)
+          .Case("fail_multi_success_overall_fail.carbon",
+                [&](TestParams&) {
+                  return HandleMultiSuccessTests(/*overall=*/false, /*a=*/true,
+                                                 /*b=*/true);
+                })
+          .Case("multi_success.carbon",
+                [&](TestParams&) {
+                  return HandleMultiSuccessTests(/*overall=*/true, /*a=*/true,
+                                                 /*b=*/true);
+                })
+          .Case("multi_success_and_fail.carbon",
+                [&](TestParams&) {
+                  return HandleMultiSuccessTests(/*overall=*/false, /*a=*/true,
+                                                 /*b=*/false);
+                })
+          .Default(&EchoFileContent);
+
+  // Call the appropriate test function for the file.
+  TestParams params = {.fs = fs, .stdout = stdout, .stderr = stderr};
+  CARBON_ASSIGN_OR_RETURN(params.files, GetFilesFromArgs(test_args, fs));
+  return test_fn(params);
+}
+
 }  // namespace
 
 CARBON_FILE_TEST_FACTORY(FileTestBaseTest)
diff --git a/testing/file_test/testdata/not_split.carbon b/testing/file_test/testdata/not_split.carbon
index 627c881d0691..21a0f8040112 100644
--- a/testing/file_test/testdata/not_split.carbon
+++ b/testing/file_test/testdata/not_split.carbon
@@ -8,4 +8,6 @@
 // TIP: To dump output, run:
 // TIP:   bazel run //testing/file_test:file_test_base_test -- --dump_output --file_tests=testing/file_test/testdata/not_split.carbon
 // CHECK:STDOUT: 2 args: `default_args`, `not_split.carbon`
-// CHECK:STDOUT: not_split.carbon:[[@LINE-10]]: starts with "// Part of the Carbon Language project, ", length 11 lines
+
+not split
+// CHECK:STDOUT: not_split.carbon:[[@LINE-1]]: not split
diff --git a/testing/file_test/testdata/replace_content.carbon b/testing/file_test/testdata/replace_content.carbon
new file mode 100644
index 000000000000..11f96c5397c9
--- /dev/null
+++ b/testing/file_test/testdata/replace_content.carbon
@@ -0,0 +1,13 @@
+// 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
+
+// AUTOUPDATE
+// TIP: To test this file alone, run:
+// TIP:   bazel test //testing/file_test:file_test_base_test --test_arg=--file_tests=testing/file_test/testdata/replace_content.carbon
+// TIP: To dump output, run:
+// TIP:   bazel run //testing/file_test:file_test_base_test -- --dump_output --file_tests=testing/file_test/testdata/replace_content.carbon
+// CHECK:STDOUT: 2 args: `default_args`, `replace_content.carbon`
+
+library "[[@TEST_NAME]]";
+// CHECK:STDOUT: replace_content.carbon:[[@LINE-1]]: library "replace_content";
diff --git a/testing/file_test/testdata/replace_split_content.carbon b/testing/file_test/testdata/replace_split_content.carbon
new file mode 100644
index 000000000000..f13fe92cb9b9
--- /dev/null
+++ b/testing/file_test/testdata/replace_split_content.carbon
@@ -0,0 +1,35 @@
+// 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
+
+// AUTOUPDATE
+// TIP: To test this file alone, run:
+// TIP:   bazel test //testing/file_test:file_test_base_test --test_arg=--file_tests=testing/file_test/testdata/replace_split_content.carbon
+// TIP: To dump output, run:
+// TIP:   bazel run //testing/file_test:file_test_base_test -- --dump_output --file_tests=testing/file_test/testdata/replace_split_content.carbon
+// CHECK:STDOUT: 6 args: `default_args`, `a.carbon`, `b.impl.carbon`, `todo_c.carbon`, `todo_fail_d.carbon`, `triplicate.carbon`
+
+// --- a.carbon
+
+library "[[@TEST_NAME]]";
+// CHECK:STDOUT: a.carbon:[[@LINE-1]]: library "a";
+
+// --- b.impl.carbon
+
+library "[[@TEST_NAME]]";
+// CHECK:STDOUT: b.impl.carbon:[[@LINE-1]]: library "b";
+
+// --- todo_c.carbon
+
+library "[[@TEST_NAME]]";
+// CHECK:STDOUT: todo_c.carbon:[[@LINE-1]]: library "c";
+
+// --- todo_fail_d.carbon
+
+library "[[@TEST_NAME]]";
+// CHECK:STDOUT: todo_fail_d.carbon:[[@LINE-1]]: library "d";
+
+// --- triplicate.carbon
+
+[[@TEST_NAME]][[@TEST_NAME]][[@TEST_NAME]]
+// CHECK:STDOUT: triplicate.carbon:[[@LINE-1]]: triplicatetriplicatetriplicate
diff --git a/testing/file_test/testdata/two_files.carbon b/testing/file_test/testdata/two_files.carbon
index b3399ffb2632..2f6cad4e88f3 100644
--- a/testing/file_test/testdata/two_files.carbon
+++ b/testing/file_test/testdata/two_files.carbon
@@ -11,8 +11,9 @@
 
 // --- a.carbon
 aaa
-// CHECK:STDOUT: a.carbon:[[@LINE-1]]: starts with "aaa\n// CHECK:STDOUT: a.carbon:{{\[\[}}@LINE-1]", length 3 lines
+// CHECK:STDOUT: a.carbon:[[@LINE-1]]: aaa
+
 
 // --- b.carbon
 bbb
-// CHECK:STDOUT: b.carbon:[[@LINE-1]]: starts with "bbb\n// CHECK:STDOUT: b.carbon:{{\[\[}}@LINE-1]", length 2 lines
+// CHECK:STDOUT: b.carbon:[[@LINE-1]]: bbb