diff --git a/WORKSPACE b/WORKSPACE
index e529175a26dc..afd95bee5cc7 100644
--- a/WORKSPACE
+++ b/WORKSPACE
@@ -89,6 +89,45 @@ load(
 
 configure_clang_toolchain(name = "bazel_cc_toolchain")
 
+###############################################################################
+# Abseil libraries
+###############################################################################
+
+abseil_version = "4a995b1eaa4a602f0d3a9ff8eac89d4649cd2fe8"
+
+http_archive(
+    name = "com_google_absl",
+    sha256 = "f5021900ff9a6b8f39406d15f460714660ab6b3e727754663d786d75ecad5ee0",
+    strip_prefix = "abseil-cpp-%s" % abseil_version,
+    urls = ["https://github.com/abseil/abseil-cpp/archive/%s.zip" % abseil_version],
+)
+
+###############################################################################
+# GoogleTest libraries
+###############################################################################
+
+googletest_version = "075810f7a20405ea09a93f68847d6e963212fa62"
+
+http_archive(
+    name = "com_google_googletest",
+    sha256 = "19949c33e795197dbb8610672c18bff447dc31faef3257665d69d1bf0884d67b",
+    strip_prefix = "googletest-%s" % googletest_version,
+    urls = ["https://github.com/google/googletest/archive/%s.zip" % googletest_version],
+)
+
+###############################################################################
+# Google Benchmark libraries
+###############################################################################
+
+benchmark_version = "0baacde3618ca617da95375e0af13ce1baadea47"
+
+http_archive(
+    name = "com_github_google_benchmark",
+    sha256 = "19949c33e795197dbb8610672c18bff447dc31faef3257665d69d1bf0884d67b",
+    strip_prefix = "benchmark-%s" % benchmark_version,
+    urls = ["https://github.com/google/benchmark/archive/%s.zip" % benchmark_version],
+)
+
 ###############################################################################
 # LLVM libraries
 ###############################################################################
diff --git a/bazel/check_deps/BUILD b/bazel/check_deps/BUILD
new file mode 100644
index 000000000000..8036552ea6c5
--- /dev/null
+++ b/bazel/check_deps/BUILD
@@ -0,0 +1,87 @@
+# 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
+
+load("@mypy_integration//:mypy.bzl", "mypy_test")
+
+# This filegroup should contain all the non-test C++ rules in the repository to
+# enable dependency checking. It can be regenerated by running the following
+# query command:
+#
+# ```
+# bazelisk query 'kind("cc.* rule", attr(testonly, 0, //...))'
+# ```
+filegroup(
+    name = "non_test_cc_rules",
+    data = [
+        "//common:check",
+        "//common:indirect_value",
+        "//common:ostream",
+        "//common:string_helpers",
+        "//executable_semantics",
+        "//executable_semantics/ast",
+        "//executable_semantics/ast:class_definition",
+        "//executable_semantics/ast:declaration",
+        "//executable_semantics/ast:expression",
+        "//executable_semantics/ast:library_name",
+        "//executable_semantics/ast:member",
+        "//executable_semantics/ast:paren_contents",
+        "//executable_semantics/ast:pattern",
+        "//executable_semantics/ast:source_location",
+        "//executable_semantics/ast:statement",
+        "//executable_semantics/common:arena",
+        "//executable_semantics/common:error",
+        "//executable_semantics/common:nonnull",
+        "//executable_semantics/interpreter",
+        "//executable_semantics/interpreter:address",
+        "//executable_semantics/interpreter:dictionary",
+        "//executable_semantics/interpreter:exec_program",
+        "//executable_semantics/interpreter:field_path",
+        "//executable_semantics/interpreter:heap",
+        "//executable_semantics/interpreter:stack",
+        "//executable_semantics/interpreter:type_checker",
+        "//executable_semantics/syntax",
+        "//executable_semantics/syntax:bison_wrap",
+        "//migrate_cpp/cpp_refactoring",
+        "//migrate_cpp/cpp_refactoring:fn_inserter",
+        "//migrate_cpp/cpp_refactoring:for_range",
+        "//migrate_cpp/cpp_refactoring:matcher",
+        "//migrate_cpp/cpp_refactoring:var_decl",
+        "//toolchain/diagnostics:diagnostic_emitter",
+        "//toolchain/diagnostics:null_diagnostics",
+        "//toolchain/driver",
+        "//toolchain/driver:carbon",
+        "//toolchain/lexer:character_set",
+        "//toolchain/lexer:numeric_literal",
+        "//toolchain/lexer:string_literal",
+        "//toolchain/lexer:token_kind",
+        "//toolchain/lexer:tokenized_buffer",
+        "//toolchain/parser:parse_node_kind",
+        "//toolchain/parser:parse_tree",
+        "//toolchain/parser:precedence",
+        "//toolchain/source:source_buffer",
+    ],
+)
+
+genquery(
+    name = "non_test_cc_deps.txt",
+    expression = "kind('cc.* rule', deps(//bazel/check_deps:non_test_cc_rules))",
+    opts = [
+        "--notool_deps",
+        "--noimplicit_deps",
+    ],
+    scope = [":non_test_cc_rules"],
+)
+
+py_test(
+    name = "check_non_test_cc_deps",
+    srcs = ["check_non_test_cc_deps.py"],
+    data = [":non_test_cc_deps.txt"],
+    main = "check_non_test_cc_deps.py",
+)
+
+mypy_test(
+    name = "check_non_test_cc_deps_mypy_test",
+    include_imports = True,
+    deps = [":check_non_test_cc_deps"],
+)
diff --git a/bazel/check_deps/check_non_test_cc_deps.py b/bazel/check_deps/check_non_test_cc_deps.py
new file mode 100644
index 000000000000..7a0f26d6cc5a
--- /dev/null
+++ b/bazel/check_deps/check_non_test_cc_deps.py
@@ -0,0 +1,74 @@
+#!/usr/bin/env python3
+
+"""Check that non-test C++ rules only depend on Carbon and LLVM.
+
+Carbon works to ensure its user-visible libraries and binaries only depend on
+their code and LLVM. Among other benefits, this provides a single, simple
+license used for the whole project.
+
+However, we frequently use third-party projects and libraries where useful in
+our test code. Here, we verify that the dependencies of non-test C++ rules only
+include Carbon and LLVM code.
+"""
+
+__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 os
+import sys
+from pathlib import Path
+
+runfiles = Path(os.environ["TEST_SRCDIR"])
+deps_path = (
+    runfiles / "carbon" / "bazel" / "check_deps" / "non_test_cc_deps.txt"
+)
+try:
+    with deps_path.open() as deps_file:
+        deps = deps_file.read().splitlines()
+except FileNotFoundError:
+    sys.exit("ERROR: unable to find deps file: %s" % deps_path)
+
+for dep in deps:
+    print("Checking dependency: " + dep)
+    repo, _, rule = dep.partition("//")
+    if repo == "" and not rule.startswith("third_party"):
+        # Carbon code is always allowed.
+        continue
+    if repo == "@llvm-project":
+        package, _, rule = rule.partition(":")
+
+        # Other packages in the LLVM project shouldn't be accidentally used
+        # in Carbon. We can expand the above list if use cases emerge.
+        if package not in ("llvm", "lld", "clang"):
+            sys.exit(
+                "ERROR: unexpected dependency into the LLVM project: %s" % dep
+            )
+
+        # Check for accidentally using the copy of GoogleTest in LLVM.
+        if rule in ("gmock", "gtest", "gtest_main"):
+            sys.exit(
+                "ERROR: dependency on LLVM's GoogleTest from non-test code: %s"
+                % dep
+            )
+
+        # The rest of LLVM, LLD, and Clang themselves are safe to depend on.
+        continue
+    if repo in ("@llvm_terminfo", "@llvm_zlib"):
+        # These are stubs wrapping system libraries for LLVM. They aren't
+        # distributed and so should be fine.
+        continue
+    if repo in (
+        "@com_google_absl",
+        "@com_google_googletest",
+        "@com_github_google_benchmark",
+    ):
+        # This should never be reached from non-test code, but these targets do
+        # exist. Specially diagnose them to try to provide a more helpful
+        # message.
+        sys.exit("ERROR: dependency only allowed in test code: %s" % dep)
+
+    # Conservatively fail if a dependency isn't explicitly allowed above.
+    sys.exit("ERROR: unknown dependency: %s" % dep)
diff --git a/common/BUILD b/common/BUILD
index 001140b9e099..8a0ff09c4de8 100644
--- a/common/BUILD
+++ b/common/BUILD
@@ -18,8 +18,7 @@ cc_test(
     srcs = ["check_test.cpp"],
     deps = [
         ":check",
-        "@llvm-project//llvm:gtest",
-        "@llvm-project//llvm:gtest_main",
+        "@com_google_googletest//:gtest_main",
     ],
 )
 
@@ -33,8 +32,7 @@ cc_test(
     srcs = ["indirect_value_test.cpp"],
     deps = [
         ":indirect_value",
-        "@llvm-project//llvm:gtest",
-        "@llvm-project//llvm:gtest_main",
+        "@com_google_googletest//:gtest_main",
     ],
 )
 
@@ -61,7 +59,6 @@ cc_test(
     srcs = ["string_helpers_test.cpp"],
     deps = [
         ":string_helpers",
-        "@llvm-project//llvm:gtest",
-        "@llvm-project//llvm:gtest_main",
+        "@com_google_googletest//:gtest_main",
     ],
 )
diff --git a/common/check_test.cpp b/common/check_test.cpp
index abc289546526..d17ff5cffa4d 100644
--- a/common/check_test.cpp
+++ b/common/check_test.cpp
@@ -4,7 +4,7 @@
 
 #include "common/check.h"
 
-#include "gtest/gtest.h"
+#include <gtest/gtest.h>
 
 namespace Carbon {
 
diff --git a/common/indirect_value_test.cpp b/common/indirect_value_test.cpp
index b9f903e69cc7..9263578e3dbd 100644
--- a/common/indirect_value_test.cpp
+++ b/common/indirect_value_test.cpp
@@ -4,9 +4,9 @@
 
 #include "common/indirect_value.h"
 
-#include <string>
+#include <gtest/gtest.h>
 
-#include "gtest/gtest.h"
+#include <string>
 
 namespace Carbon {
 namespace {
diff --git a/common/ostream.h b/common/ostream.h
index 1920a82493c5..5378279eb2b7 100644
--- a/common/ostream.h
+++ b/common/ostream.h
@@ -5,11 +5,14 @@
 #ifndef COMMON_OSTREAM_H_
 #define COMMON_OSTREAM_H_
 
+#include <ostream>
+
+#include "llvm/Support/raw_os_ostream.h"
 #include "llvm/Support/raw_ostream.h"
 
 namespace Carbon {
 
-// Support ostream << for types which implement:
+// Support raw_ostream << for types which implement:
 //   void Print(llvm::raw_ostream& out) const;
 template <typename T, typename std::enable_if<std::is_member_function_pointer<
                           decltype(&T::Print)>::value>::type* = nullptr>
@@ -18,7 +21,7 @@ auto operator<<(llvm::raw_ostream& out, const T& obj) -> llvm::raw_ostream& {
   return out;
 }
 
-// Prevents ostream << for pointers to printable types.
+// Prevents raw_ostream << for pointers to printable types.
 template <typename T, typename std::enable_if<std::is_member_function_pointer<
                           decltype(&T::Print)>::value>::type* = nullptr>
 __attribute__((unavailable(
@@ -26,6 +29,67 @@ __attribute__((unavailable(
     "To print as a pointer, cast to void*."))) auto
 operator<<(llvm::raw_ostream& out, const T* /*obj*/) -> llvm::raw_ostream&;
 
+// Support std::ostream << for types which implement:
+//   void Print(llvm::raw_ostream& out) const;
+template <typename T, typename std::enable_if<std::is_member_function_pointer<
+                          decltype(&T::Print)>::value>::type* = nullptr>
+auto operator<<(std::ostream& out, const T& obj) -> std::ostream& {
+  llvm::raw_os_ostream raw_os(out);
+  obj.Print(raw_os);
+  return out;
+}
+
+// Prevents std::ostream << for pointers to printable types.
+template <typename T, typename std::enable_if<std::is_member_function_pointer<
+                          decltype(&T::Print)>::value>::type* = nullptr>
+__attribute__((unavailable(
+    "Received a pointer to a printable type, are you missing a `*`? "
+    "To print as a pointer, cast to void*."))) auto
+operator<<(std::ostream& out, const T* /*obj*/) -> std::ostream&;
+
+// Allow GoogleTest and GoogleMock to print even pointers by dereferencing them.
+// This is important to allow automatic printing of arguments of mocked APIs.
+template <typename T, typename std::enable_if<std::is_member_function_pointer<
+                          decltype(&T::Print)>::value>::type* = nullptr>
+void PrintTo(const T* p, std::ostream* out) {
+  *out << static_cast<const void*>(p);
+
+  // Also print the object if non-null.
+  if (p) {
+    *out << " pointing to " << *p;
+  }
+}
+
 }  // namespace Carbon
 
+namespace llvm {
+
+// Injects an `operator<<` overload into the `llvm` namespace which detects LLVM
+// types with `raw_ostream` overloads and uses that to map to a `std::ostream`
+// overload. This allows LLVM types to be printed to `std::ostream` via their
+// `raw_ostream` operator overloads, which is needed both for logging and
+// testing.
+//
+// To make this overload be unusually low priority, it is designed to take even
+// the `std::ostream` parameter as a template, and SFINAE disable itself unless
+// that template parameter matches `std::ostream`. This ensures that an
+// *explicit* operator will be preferred when provided. Some LLVM types may have
+// this, and so we want to prioritize accordingly.
+//
+// It would be slightly cleaner for LLVM itself to provide this overload in
+// `raw_os_ostream.h` so that we wouldn't need to inject into its namespace, but
+// supporting `std::ostream` isn't a priority for LLVM so we handle it locally
+// instead.
+template <typename S, typename T,
+          typename = std::enable_if_t<std::is_base_of_v<
+              std::ostream, std::remove_reference_t<std::remove_cv_t<S>>>>,
+          typename = std::enable_if_t<!std::is_same_v<
+              std::remove_reference_t<std::remove_cv_t<T>>, raw_ostream>>>
+auto operator<<(S& standard_out, const T& value) -> S& {
+  raw_os_ostream(standard_out) << value;
+  return standard_out;
+}
+
+}  // namespace llvm
+
 #endif  // COMMON_OSTREAM_H_
diff --git a/common/string_helpers_test.cpp b/common/string_helpers_test.cpp
index 3a21772270ef..0d91945c281a 100644
--- a/common/string_helpers_test.cpp
+++ b/common/string_helpers_test.cpp
@@ -4,10 +4,10 @@
 
 #include "common/string_helpers.h"
 
-#include <string>
+#include <gmock/gmock.h>
+#include <gtest/gtest.h>
 
-#include "gmock/gmock.h"
-#include "gtest/gtest.h"
+#include <string>
 
 using ::testing::Eq;
 using ::testing::Optional;
diff --git a/compile_flags.txt b/compile_flags.txt
index b9d01a5d249c..91e03d586dd4 100644
--- a/compile_flags.txt
+++ b/compile_flags.txt
@@ -37,7 +37,6 @@
 -DGTEST_HAS_RTTI=0
 -D__STDC_LIMIT_MACROS
 -D__STDC_CONSTANT_MACROS
--DGTEST_USE_OWN_TR1_TUPLE=1
 -iquote
 .
 -iquote
@@ -62,19 +61,26 @@ bazel-bin/external/llvm_zlib
 bazel-execroot/external/bazel_tools
 -iquote
 bazel-bin/external/bazel_tools
--Ibazel-execroot/external/llvm-project/llvm/utils/unittest/googletest/src
 -isystem
 bazel-execroot/external/llvm-project/llvm/include
 -isystem
 bazel-bin/external/llvm-project/llvm/include
 -isystem
-bazel-execroot/external/llvm-project/llvm/utils/unittest/googlemock/include
+bazel-execroot/external/com_google_googletest/googlemock
 -isystem
-bazel-bin/external/llvm-project/llvm/utils/unittest/googlemock/include
+bazel-bin/external/com_google_googletest/googlemock
 -isystem
-bazel-execroot/external/llvm-project/llvm/utils/unittest/googletest/include
+bazel-execroot/external/com_google_googletest/googlemock/include
 -isystem
-bazel-bin/external/llvm-project/llvm/utils/unittest/googletest/include
+bazel-bin/external/com_google_googletest/googlemock/include
+-isystem
+bazel-execroot/external/com_google_googletest/googletest
+-isystem
+bazel-bin/external/com_google_googletest/googletest
+-isystem
+bazel-execroot/external/com_google_googletest/googletest/include
+-isystem
+bazel-bin/external/com_google_googletest/googletest/include
 -std=c++17
 -stdlib=libc++
 -no-canonical-prefixes
diff --git a/executable_semantics/BUILD b/executable_semantics/BUILD
index dc6e9a1351d9..295486a3c7d9 100644
--- a/executable_semantics/BUILD
+++ b/executable_semantics/BUILD
@@ -4,6 +4,11 @@
 
 load("//bazel/testing:lit_test.bzl", "lit_test")
 
+package(default_visibility = [
+    "//bazel/check_deps:__pkg__",
+    "//executable_semantics:__subpackages__",
+])
+
 cc_binary(
     name = "executable_semantics",
     srcs = ["main.cpp"],
diff --git a/executable_semantics/ast/BUILD b/executable_semantics/ast/BUILD
index c0b81782460a..b4f284e7d12e 100644
--- a/executable_semantics/ast/BUILD
+++ b/executable_semantics/ast/BUILD
@@ -2,7 +2,10 @@
 # Exceptions. See /LICENSE for license information.
 # SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
-package(default_visibility = ["//executable_semantics:__subpackages__"])
+package(default_visibility = [
+    "//bazel/check_deps:__pkg__",
+    "//executable_semantics:__subpackages__",
+])
 
 cc_library(
     name = "ast",
@@ -62,8 +65,7 @@ cc_test(
     deps = [
         ":expression",
         ":paren_contents",
-        "@llvm-project//llvm:gtest",
-        "@llvm-project//llvm:gtest_main",
+        "@com_google_googletest//:gtest_main",
     ],
 )
 
@@ -112,9 +114,8 @@ cc_test(
     deps = [
         ":paren_contents",
         ":pattern",
+        "@com_google_googletest//:gtest_main",
         "@llvm-project//llvm:Support",
-        "@llvm-project//llvm:gtest",
-        "@llvm-project//llvm:gtest_main",
     ],
 )
 
diff --git a/executable_semantics/ast/expression_test.cpp b/executable_semantics/ast/expression_test.cpp
index 11b759c030fe..95ca49323020 100644
--- a/executable_semantics/ast/expression_test.cpp
+++ b/executable_semantics/ast/expression_test.cpp
@@ -4,12 +4,13 @@
 
 #include "executable_semantics/ast/expression.h"
 
+#include <gmock/gmock.h>
+#include <gtest/gtest.h>
+
 #include <string>
 
 #include "executable_semantics/ast/paren_contents.h"
 #include "executable_semantics/common/arena.h"
-#include "gmock/gmock.h"
-#include "gtest/gtest.h"
 #include "llvm/Support/Casting.h"
 
 namespace Carbon {
diff --git a/executable_semantics/ast/pattern_test.cpp b/executable_semantics/ast/pattern_test.cpp
index d7b23a32deba..e52cb35503d8 100644
--- a/executable_semantics/ast/pattern_test.cpp
+++ b/executable_semantics/ast/pattern_test.cpp
@@ -4,11 +4,12 @@
 
 #include "executable_semantics/ast/pattern.h"
 
+#include <gmock/gmock.h>
+#include <gtest/gtest.h>
+
 #include "executable_semantics/ast/expression.h"
 #include "executable_semantics/ast/paren_contents.h"
 #include "executable_semantics/common/arena.h"
-#include "gmock/gmock.h"
-#include "gtest/gtest.h"
 #include "llvm/Support/Casting.h"
 
 namespace Carbon {
diff --git a/executable_semantics/common/BUILD b/executable_semantics/common/BUILD
index e17d835e8634..1c58953f1b91 100644
--- a/executable_semantics/common/BUILD
+++ b/executable_semantics/common/BUILD
@@ -2,7 +2,10 @@
 # Exceptions. See /LICENSE for license information.
 # SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
-package(default_visibility = ["//executable_semantics:__subpackages__"])
+package(default_visibility = [
+    "//bazel/check_deps:__pkg__",
+    "//executable_semantics:__subpackages__",
+])
 
 cc_library(
     name = "arena",
@@ -25,8 +28,7 @@ cc_test(
     srcs = ["error_test.cpp"],
     deps = [
         ":error",
-        "@llvm-project//llvm:gtest",
-        "@llvm-project//llvm:gtest_main",
+        "@com_google_googletest//:gtest_main",
     ],
 )
 
diff --git a/executable_semantics/common/error_test.cpp b/executable_semantics/common/error_test.cpp
index d125b54b14de..46a7daae82cd 100644
--- a/executable_semantics/common/error_test.cpp
+++ b/executable_semantics/common/error_test.cpp
@@ -4,7 +4,7 @@
 
 #include "executable_semantics/common/error.h"
 
-#include "gtest/gtest.h"
+#include <gtest/gtest.h>
 
 namespace Carbon {
 namespace {
diff --git a/executable_semantics/interpreter/BUILD b/executable_semantics/interpreter/BUILD
index 0a760e301a61..bc29b83543b4 100644
--- a/executable_semantics/interpreter/BUILD
+++ b/executable_semantics/interpreter/BUILD
@@ -2,7 +2,10 @@
 # Exceptions. See /LICENSE for license information.
 # SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
-package(default_visibility = ["//executable_semantics:__pkg__"])
+package(default_visibility = [
+    "//bazel/check_deps:__pkg__",
+    "//executable_semantics:__pkg__",
+])
 
 # These currently have to be a single build rule because of a dependency cycle
 # in printing.
diff --git a/executable_semantics/syntax/BUILD b/executable_semantics/syntax/BUILD
index e0f654c0eac5..92cc2025d7fd 100644
--- a/executable_semantics/syntax/BUILD
+++ b/executable_semantics/syntax/BUILD
@@ -4,7 +4,10 @@
 
 load("@mypy_integration//:mypy.bzl", "mypy_test")
 
-package(default_visibility = ["//executable_semantics:__pkg__"])
+package(default_visibility = [
+    "//bazel/check_deps:__pkg__",
+    "//executable_semantics:__pkg__",
+])
 
 cc_library(
     name = "bison_wrap",
diff --git a/migrate_cpp/cpp_refactoring/BUILD b/migrate_cpp/cpp_refactoring/BUILD
index 8a233b710d80..0deb1406bd6b 100644
--- a/migrate_cpp/cpp_refactoring/BUILD
+++ b/migrate_cpp/cpp_refactoring/BUILD
@@ -34,10 +34,9 @@ cc_library(
     hdrs = ["matcher_test_base.h"],
     deps = [
         ":matcher",
+        "@com_google_googletest//:gtest",
         "@llvm-project//clang:ast_matchers",
         "@llvm-project//clang:tooling",
-        "@llvm-project//llvm:gmock",
-        "@llvm-project//llvm:gtest",
     ],
 )
 
@@ -56,8 +55,8 @@ cc_test(
     deps = [
         ":fn_inserter",
         ":matcher_test_base",
+        "@com_google_googletest//:gtest_main",
         "@llvm-project//clang:tooling",
-        "@llvm-project//llvm:gtest_main",
     ],
 )
 
@@ -74,8 +73,8 @@ cc_test(
     deps = [
         ":for_range",
         ":matcher_test_base",
+        "@com_google_googletest//:gtest_main",
         "@llvm-project//clang:tooling",
-        "@llvm-project//llvm:gtest_main",
     ],
 )
 
@@ -92,7 +91,7 @@ cc_test(
     deps = [
         ":matcher_test_base",
         ":var_decl",
+        "@com_google_googletest//:gtest_main",
         "@llvm-project//clang:tooling",
-        "@llvm-project//llvm:gtest_main",
     ],
 )
diff --git a/migrate_cpp/cpp_refactoring/matcher_test_base.h b/migrate_cpp/cpp_refactoring/matcher_test_base.h
index d0f51ca0878f..9d0e70565721 100644
--- a/migrate_cpp/cpp_refactoring/matcher_test_base.h
+++ b/migrate_cpp/cpp_refactoring/matcher_test_base.h
@@ -5,11 +5,12 @@
 #ifndef MIGRATE_CPP_CPP_REFACTORING_MATCHER_TEST_BASE_H_
 #define MIGRATE_CPP_CPP_REFACTORING_MATCHER_TEST_BASE_H_
 
+#include <gmock/gmock.h>
+#include <gtest/gtest.h>
+
 #include "clang/ASTMatchers/ASTMatchFinder.h"
 #include "clang/Tooling/Core/Replacement.h"
 #include "clang/Tooling/Tooling.h"
-#include "gmock/gmock.h"
-#include "gtest/gtest.h"
 #include "migrate_cpp/cpp_refactoring/matcher_manager.h"
 
 namespace Carbon {
diff --git a/toolchain/common/BUILD b/toolchain/common/BUILD
index 21c8ed865e5d..0bbde85550a9 100644
--- a/toolchain/common/BUILD
+++ b/toolchain/common/BUILD
@@ -10,7 +10,7 @@ cc_library(
     srcs = ["yaml_test_helpers.cpp"],
     hdrs = ["yaml_test_helpers.h"],
     deps = [
-        "@llvm-project//llvm:gmock",
-        "@llvm-project//llvm:gtest",
+        "//common:ostream",
+        "@com_google_googletest//:gtest",
     ],
 )
diff --git a/toolchain/common/yaml_test_helpers.cpp b/toolchain/common/yaml_test_helpers.cpp
index 58380c0f1a28..46aceaae52ad 100644
--- a/toolchain/common/yaml_test_helpers.cpp
+++ b/toolchain/common/yaml_test_helpers.cpp
@@ -4,6 +4,7 @@
 
 #include "toolchain/common/yaml_test_helpers.h"
 
+#include "llvm/ADT/SmallString.h"
 #include "llvm/Support/YAMLParser.h"
 
 namespace Carbon::Testing::Yaml {
diff --git a/toolchain/common/yaml_test_helpers.h b/toolchain/common/yaml_test_helpers.h
index 058168fd26fc..eeb78d9288ff 100644
--- a/toolchain/common/yaml_test_helpers.h
+++ b/toolchain/common/yaml_test_helpers.h
@@ -47,13 +47,15 @@
 #ifndef TOOLCHAIN_COMMON_YAML_TEST_HELPERS_H_
 #define TOOLCHAIN_COMMON_YAML_TEST_HELPERS_H_
 
+#include <gmock/gmock.h>
+#include <gtest/gtest.h>
+
 #include <iomanip>
 #include <iostream>
 #include <sstream>
 #include <variant>
 
-#include "gmock/gmock.h"
-#include "gtest/gtest.h"
+#include "common/ostream.h"
 
 namespace Carbon {
 namespace Testing {
diff --git a/toolchain/diagnostics/BUILD b/toolchain/diagnostics/BUILD
index 5752e35f62ab..9af2df3866b3 100644
--- a/toolchain/diagnostics/BUILD
+++ b/toolchain/diagnostics/BUILD
@@ -26,8 +26,8 @@ cc_library(
     hdrs = ["mocks.h"],
     deps = [
         ":diagnostic_emitter",
+        "@com_google_googletest//:gtest",
         "@llvm-project//llvm:Support",
-        "@llvm-project//llvm:gmock",
     ],
 )
 
@@ -37,9 +37,7 @@ cc_test(
     deps = [
         ":diagnostic_emitter",
         ":mocks",
+        "@com_google_googletest//:gtest_main",
         "@llvm-project//llvm:Support",
-        "@llvm-project//llvm:gmock",
-        "@llvm-project//llvm:gtest",
-        "@llvm-project//llvm:gtest_main",
     ],
 )
diff --git a/toolchain/diagnostics/diagnostic_emitter_test.cpp b/toolchain/diagnostics/diagnostic_emitter_test.cpp
index 2a3be968a4ee..7783d55b9ff3 100644
--- a/toolchain/diagnostics/diagnostic_emitter_test.cpp
+++ b/toolchain/diagnostics/diagnostic_emitter_test.cpp
@@ -4,8 +4,9 @@
 
 #include "toolchain/diagnostics/diagnostic_emitter.h"
 
-#include "gmock/gmock.h"
-#include "gtest/gtest.h"
+#include <gmock/gmock.h>
+#include <gtest/gtest.h>
+
 #include "llvm/ADT/StringRef.h"
 #include "llvm/Support/FormatVariadic.h"
 #include "toolchain/diagnostics/mocks.h"
diff --git a/toolchain/diagnostics/mocks.h b/toolchain/diagnostics/mocks.h
index dd611e0a27e2..abecee576ec0 100644
--- a/toolchain/diagnostics/mocks.h
+++ b/toolchain/diagnostics/mocks.h
@@ -5,7 +5,8 @@
 #ifndef TOOLCHAIN_DIAGNOSTICS_MOCKS_H_
 #define TOOLCHAIN_DIAGNOSTICS_MOCKS_H_
 
-#include "gmock/gmock.h"
+#include <gmock/gmock.h>
+
 #include "toolchain/diagnostics/diagnostic_emitter.h"
 
 namespace Carbon {
diff --git a/toolchain/driver/BUILD b/toolchain/driver/BUILD
index 6705938f3b4b..782700c095a5 100644
--- a/toolchain/driver/BUILD
+++ b/toolchain/driver/BUILD
@@ -27,10 +27,8 @@ cc_test(
         ":driver",
         "//toolchain/common:yaml_test_helpers",
         "//toolchain/lexer:tokenized_buffer_test_helpers",
+        "@com_google_googletest//:gtest_main",
         "@llvm-project//llvm:Support",
-        "@llvm-project//llvm:gmock",
-        "@llvm-project//llvm:gtest",
-        "@llvm-project//llvm:gtest_main",
     ],
 )
 
diff --git a/toolchain/driver/driver_test.cpp b/toolchain/driver/driver_test.cpp
index 7202b41ba63a..dc546e5cc724 100644
--- a/toolchain/driver/driver_test.cpp
+++ b/toolchain/driver/driver_test.cpp
@@ -4,8 +4,9 @@
 
 #include "toolchain/driver/driver.h"
 
-#include "gmock/gmock.h"
-#include "gtest/gtest.h"
+#include <gmock/gmock.h>
+#include <gtest/gtest.h>
+
 #include "llvm/ADT/SmallString.h"
 #include "llvm/Support/FileSystem.h"
 #include "llvm/Support/SourceMgr.h"
diff --git a/toolchain/lexer/BUILD b/toolchain/lexer/BUILD
index 295aadb1aa33..1881ae66fb9d 100644
--- a/toolchain/lexer/BUILD
+++ b/toolchain/lexer/BUILD
@@ -19,9 +19,8 @@ cc_test(
     srcs = ["token_kind_test.cpp"],
     deps = [
         ":token_kind",
+        "@com_google_googletest//:gtest_main",
         "@llvm-project//llvm:Support",
-        "@llvm-project//llvm:gtest",
-        "@llvm-project//llvm:gtest_main",
     ],
 )
 
@@ -58,11 +57,10 @@ cc_test(
     deps = [
         ":numeric_literal",
         ":test_helpers",
+        "//common:ostream",
         "//toolchain/diagnostics:diagnostic_emitter",
+        "@com_google_googletest//:gtest_main",
         "@llvm-project//llvm:Support",
-        "@llvm-project//llvm:gmock",
-        "@llvm-project//llvm:gtest",
-        "@llvm-project//llvm:gtest_main",
     ],
 )
 
@@ -95,11 +93,10 @@ cc_test(
     deps = [
         ":string_literal",
         ":test_helpers",
+        "//common:ostream",
         "//toolchain/diagnostics:diagnostic_emitter",
+        "@com_google_googletest//:gtest_main",
         "@llvm-project//llvm:Support",
-        "@llvm-project//llvm:gmock",
-        "@llvm-project//llvm:gtest",
-        "@llvm-project//llvm:gtest_main",
     ],
 )
 
@@ -124,6 +121,7 @@ cc_library(
         ":numeric_literal",
         ":string_literal",
         ":token_kind",
+        "//common:ostream",
         "//toolchain/diagnostics:diagnostic_emitter",
         "//toolchain/source:source_buffer",
         "@llvm-project//llvm:Support",
@@ -136,8 +134,8 @@ cc_library(
     hdrs = ["tokenized_buffer_test_helpers.h"],
     deps = [
         ":tokenized_buffer",
+        "@com_google_googletest//:gtest",
         "@llvm-project//llvm:Support",
-        "@llvm-project//llvm:gmock",
     ],
 )
 
@@ -150,10 +148,8 @@ cc_test(
         "//toolchain/common:yaml_test_helpers",
         "//toolchain/diagnostics:diagnostic_emitter",
         "//toolchain/diagnostics:mocks",
+        "@com_google_googletest//:gtest_main",
         "@llvm-project//llvm:Support",
-        "@llvm-project//llvm:gmock",
-        "@llvm-project//llvm:gtest",
-        "@llvm-project//llvm:gtest_main",
     ],
 )
 
diff --git a/toolchain/lexer/numeric_literal_test.cpp b/toolchain/lexer/numeric_literal_test.cpp
index ee0fb48fe1e7..b69227b28939 100644
--- a/toolchain/lexer/numeric_literal_test.cpp
+++ b/toolchain/lexer/numeric_literal_test.cpp
@@ -4,12 +4,14 @@
 
 #include "toolchain/lexer/numeric_literal.h"
 
+#include <gmock/gmock.h>
+#include <gtest/gtest.h>
+
 #include <iterator>
 #include <memory>
 #include <vector>
 
-#include "gmock/gmock.h"
-#include "gtest/gtest.h"
+#include "common/ostream.h"
 #include "toolchain/diagnostics/diagnostic_emitter.h"
 #include "toolchain/lexer/test_helpers.h"
 
diff --git a/toolchain/lexer/string_literal_test.cpp b/toolchain/lexer/string_literal_test.cpp
index 897a7ce8bb04..34e097f5ef69 100644
--- a/toolchain/lexer/string_literal_test.cpp
+++ b/toolchain/lexer/string_literal_test.cpp
@@ -4,8 +4,10 @@
 
 #include "toolchain/lexer/string_literal.h"
 
-#include "gmock/gmock.h"
-#include "gtest/gtest.h"
+#include <gmock/gmock.h>
+#include <gtest/gtest.h>
+
+#include "common/ostream.h"
 #include "toolchain/diagnostics/diagnostic_emitter.h"
 #include "toolchain/lexer/test_helpers.h"
 
diff --git a/toolchain/lexer/token_kind_test.cpp b/toolchain/lexer/token_kind_test.cpp
index 0ef6f276ea2f..4b8b1a1f6456 100644
--- a/toolchain/lexer/token_kind_test.cpp
+++ b/toolchain/lexer/token_kind_test.cpp
@@ -4,10 +4,11 @@
 
 #include "toolchain/lexer/token_kind.h"
 
+#include <gmock/gmock.h>
+#include <gtest/gtest.h>
+
 #include <cstring>
 
-#include "gmock/gmock.h"
-#include "gtest/gtest.h"
 #include "llvm/ADT/StringRef.h"
 
 namespace Carbon {
diff --git a/toolchain/lexer/tokenized_buffer.cpp b/toolchain/lexer/tokenized_buffer.cpp
index 08db26a50b71..dee67fd23edb 100644
--- a/toolchain/lexer/tokenized_buffer.cpp
+++ b/toolchain/lexer/tokenized_buffer.cpp
@@ -863,6 +863,11 @@ auto TokenizedBuffer::AddToken(TokenInfo info) -> Token {
   return Token(static_cast<int>(token_infos.size()) - 1);
 }
 
+auto TokenizedBuffer::TokenIterator::Print(llvm::raw_ostream& output) const
+    -> void {
+  output << token.index;
+}
+
 auto TokenizedBuffer::SourceBufferLocationTranslator::GetLocation(
     const char* loc) -> Diagnostic::Location {
   assert(llvm::is_sorted(std::array{buffer_->source->Text().begin(), loc,
diff --git a/toolchain/lexer/tokenized_buffer.h b/toolchain/lexer/tokenized_buffer.h
index 02aef7bdec48..cca5edcbcfc6 100644
--- a/toolchain/lexer/tokenized_buffer.h
+++ b/toolchain/lexer/tokenized_buffer.h
@@ -8,6 +8,7 @@
 #include <cstdint>
 #include <iterator>
 
+#include "common/ostream.h"
 #include "llvm/ADT/APInt.h"
 #include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/Optional.h"
@@ -15,6 +16,7 @@
 #include "llvm/ADT/StringRef.h"
 #include "llvm/ADT/iterator.h"
 #include "llvm/ADT/iterator_range.h"
+#include "llvm/Support/raw_ostream.h"
 #include "toolchain/diagnostics/diagnostic_emitter.h"
 #include "toolchain/lexer/token_kind.h"
 #include "toolchain/source/source_buffer.h"
@@ -195,6 +197,9 @@ class TokenizedBuffer {
       return *this;
     }
 
+    // Prints the raw token index.
+    auto Print(llvm::raw_ostream& output) const -> void;
+
    private:
     friend class TokenizedBuffer;
 
diff --git a/toolchain/lexer/tokenized_buffer_test.cpp b/toolchain/lexer/tokenized_buffer_test.cpp
index 70aa242aca0d..2039becc1e87 100644
--- a/toolchain/lexer/tokenized_buffer_test.cpp
+++ b/toolchain/lexer/tokenized_buffer_test.cpp
@@ -4,10 +4,11 @@
 
 #include "toolchain/lexer/tokenized_buffer.h"
 
+#include <gmock/gmock.h>
+#include <gtest/gtest.h>
+
 #include <iterator>
 
-#include "gmock/gmock.h"
-#include "gtest/gtest.h"
 #include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/None.h"
 #include "llvm/ADT/Sequence.h"
diff --git a/toolchain/lexer/tokenized_buffer_test_helpers.h b/toolchain/lexer/tokenized_buffer_test_helpers.h
index 86973972d789..ec8cc2c6362b 100644
--- a/toolchain/lexer/tokenized_buffer_test_helpers.h
+++ b/toolchain/lexer/tokenized_buffer_test_helpers.h
@@ -5,7 +5,8 @@
 #ifndef TOOLCHAIN_LEXER_TOKENIZED_BUFFER_TEST_HELPERS_H_
 #define TOOLCHAIN_LEXER_TOKENIZED_BUFFER_TEST_HELPERS_H_
 
-#include "gmock/gmock.h"
+#include <gmock/gmock.h>
+
 #include "llvm/ADT/SmallString.h"
 #include "llvm/Support/Casting.h"
 #include "llvm/Support/YAMLParser.h"
diff --git a/toolchain/parser/BUILD b/toolchain/parser/BUILD
index 6a187d7b211b..938a72ec9c3c 100644
--- a/toolchain/parser/BUILD
+++ b/toolchain/parser/BUILD
@@ -19,9 +19,8 @@ cc_test(
     srcs = ["parse_node_kind_test.cpp"],
     deps = [
         ":parse_node_kind",
+        "@com_google_googletest//:gtest_main",
         "@llvm-project//llvm:Support",
-        "@llvm-project//llvm:gtest",
-        "@llvm-project//llvm:gtest_main",
     ],
 )
 
@@ -51,8 +50,8 @@ cc_library(
         ":parse_node_kind",
         ":parse_tree",
         "//toolchain/lexer:tokenized_buffer",
+        "@com_google_googletest//:gtest",
         "@llvm-project//llvm:Support",
-        "@llvm-project//llvm:gmock",
     ],
 )
 
@@ -63,14 +62,13 @@ cc_test(
         ":parse_node_kind",
         ":parse_test_helpers",
         ":parse_tree",
+        "//common:ostream",
         "//toolchain/common:yaml_test_helpers",
         "//toolchain/diagnostics:diagnostic_emitter",
         "//toolchain/diagnostics:mocks",
         "//toolchain/lexer:tokenized_buffer",
+        "@com_google_googletest//:gtest_main",
         "@llvm-project//llvm:Support",
-        "@llvm-project//llvm:gmock",
-        "@llvm-project//llvm:gtest",
-        "@llvm-project//llvm:gtest_main",
     ],
 )
 
@@ -103,8 +101,6 @@ cc_test(
     deps = [
         ":precedence",
         "//toolchain/lexer:token_kind",
-        "@llvm-project//llvm:gmock",
-        "@llvm-project//llvm:gtest",
-        "@llvm-project//llvm:gtest_main",
+        "@com_google_googletest//:gtest_main",
     ],
 )
diff --git a/toolchain/parser/parse_node_kind_test.cpp b/toolchain/parser/parse_node_kind_test.cpp
index ae21820c1c70..74ac8a58785e 100644
--- a/toolchain/parser/parse_node_kind_test.cpp
+++ b/toolchain/parser/parse_node_kind_test.cpp
@@ -4,9 +4,10 @@
 
 #include "toolchain/parser/parse_node_kind.h"
 
+#include <gtest/gtest.h>
+
 #include <cstring>
 
-#include "gtest/gtest.h"
 #include "llvm/ADT/StringRef.h"
 
 namespace Carbon {
diff --git a/toolchain/parser/parse_test_helpers.h b/toolchain/parser/parse_test_helpers.h
index c7e3dfe86eca..ba9ec5c79939 100644
--- a/toolchain/parser/parse_test_helpers.h
+++ b/toolchain/parser/parse_test_helpers.h
@@ -5,12 +5,13 @@
 #ifndef TOOLCHAIN_PARSER_PARSE_TEST_HELPERS_H_
 #define TOOLCHAIN_PARSER_PARSE_TEST_HELPERS_H_
 
+#include <gmock/gmock.h>
+
 #include <ostream>
 #include <string>
 #include <utility>
 #include <vector>
 
-#include "gmock/gmock.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/StringRef.h"
diff --git a/toolchain/parser/parse_tree.cpp b/toolchain/parser/parse_tree.cpp
index 2314bbbb1876..16af4ca06eef 100644
--- a/toolchain/parser/parse_tree.cpp
+++ b/toolchain/parser/parse_tree.cpp
@@ -199,4 +199,18 @@ auto ParseTree::Verify() const -> bool {
   return true;
 }
 
+auto ParseTree::Node::Print(llvm::raw_ostream& output) const -> void {
+  output << GetIndex();
+}
+
+auto ParseTree::PostorderIterator::Print(llvm::raw_ostream& output) const
+    -> void {
+  output << node.GetIndex();
+}
+
+auto ParseTree::SiblingIterator::Print(llvm::raw_ostream& output) const
+    -> void {
+  output << node.GetIndex();
+}
+
 }  // namespace Carbon
diff --git a/toolchain/parser/parse_tree.h b/toolchain/parser/parse_tree.h
index c6638e639f57..50d30a76fef8 100644
--- a/toolchain/parser/parse_tree.h
+++ b/toolchain/parser/parse_tree.h
@@ -7,10 +7,12 @@
 
 #include <iterator>
 
+#include "common/ostream.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/ADT/iterator.h"
 #include "llvm/ADT/iterator_range.h"
+#include "llvm/Support/raw_ostream.h"
 #include "toolchain/diagnostics/diagnostic_emitter.h"
 #include "toolchain/lexer/tokenized_buffer.h"
 #include "toolchain/parser/parse_node_kind.h"
@@ -249,6 +251,9 @@ class ParseTree::Node {
   // FIXME: Maybe we can switch to stream operator overloads?
   [[nodiscard]] auto GetIndex() const -> int { return index; }
 
+  // Prints the node index.
+  auto Print(llvm::raw_ostream& output) const -> void;
+
  private:
   friend ParseTree;
   friend Parser;
@@ -298,6 +303,9 @@ class ParseTree::PostorderIterator
     return *this;
   }
 
+  // Prints the underlying node index.
+  auto Print(llvm::raw_ostream& output) const -> void;
+
  private:
   friend class ParseTree;
 
@@ -340,6 +348,9 @@ class ParseTree::SiblingIterator
     return *this;
   }
 
+  // Prints the underlying node index.
+  auto Print(llvm::raw_ostream& output) const -> void;
+
  private:
   friend class ParseTree;
 
diff --git a/toolchain/parser/parse_tree_test.cpp b/toolchain/parser/parse_tree_test.cpp
index 9e1f66773bfd..d6562dac3de6 100644
--- a/toolchain/parser/parse_tree_test.cpp
+++ b/toolchain/parser/parse_tree_test.cpp
@@ -4,10 +4,12 @@
 
 #include "toolchain/parser/parse_tree.h"
 
+#include <gmock/gmock.h>
+#include <gtest/gtest.h>
+
 #include <forward_list>
 
-#include "gmock/gmock.h"
-#include "gtest/gtest.h"
+#include "common/ostream.h"
 #include "llvm/ADT/Sequence.h"
 #include "llvm/Support/SourceMgr.h"
 #include "toolchain/common/yaml_test_helpers.h"
diff --git a/toolchain/parser/precedence_test.cpp b/toolchain/parser/precedence_test.cpp
index 252bf2794da6..896a35a6d928 100644
--- a/toolchain/parser/precedence_test.cpp
+++ b/toolchain/parser/precedence_test.cpp
@@ -4,8 +4,9 @@
 
 #include "toolchain/parser/precedence.h"
 
-#include "gmock/gmock.h"
-#include "gtest/gtest.h"
+#include <gmock/gmock.h>
+#include <gtest/gtest.h>
+
 #include "toolchain/lexer/token_kind.h"
 
 namespace Carbon {
diff --git a/toolchain/source/BUILD b/toolchain/source/BUILD
index 8e3eaaf79bec..aa30ad97668c 100644
--- a/toolchain/source/BUILD
+++ b/toolchain/source/BUILD
@@ -16,9 +16,7 @@ cc_test(
     srcs = ["source_buffer_test.cpp"],
     deps = [
         ":source_buffer",
+        "@com_google_googletest//:gtest_main",
         "@llvm-project//llvm:Support",
-        "@llvm-project//llvm:gmock",
-        "@llvm-project//llvm:gtest",
-        "@llvm-project//llvm:gtest_main",
     ],
 )
diff --git a/toolchain/source/source_buffer_test.cpp b/toolchain/source/source_buffer_test.cpp
index 8ef07e97ef97..e131c73fb49b 100644
--- a/toolchain/source/source_buffer_test.cpp
+++ b/toolchain/source/source_buffer_test.cpp
@@ -4,7 +4,8 @@
 
 #include "toolchain/source/source_buffer.h"
 
-#include "gtest/gtest.h"
+#include <gtest/gtest.h>
+
 #include "llvm/ADT/SmallString.h"
 #include "llvm/ADT/Twine.h"
 #include "llvm/Support/FileSystem.h"
@@ -49,7 +50,7 @@ TEST(SourceBufferTest, FileRep) {
 
   auto expected_buffer = SourceBuffer::CreateFromFile(test_file_path);
   ASSERT_TRUE(static_cast<bool>(expected_buffer))
-      << "Error message: " << expected_buffer.takeError();
+      << "Error message: " << toString(expected_buffer.takeError());
 
   SourceBuffer& buffer = *expected_buffer;