[test] Move single-threaded platform cctest to unittests

Also add a mixin for using the single-threaded default platform instead
of swapping it in with SetPlatformForTesting.

Bug: v8:12781
Change-Id: I304303e58ed713e5558d108cd7eb826c17abb40f
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3574553
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Auto-Submit: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Commit-Queue: Camillo Bruni <cbruni@chromium.org>
Cr-Commit-Position: refs/heads/main@{#79829}

test/cctest/test-api.cc

@@ -29492,38 +29492,6 @@ TEST(CodeLikeFunction) {
   ExpectInt32("new Function(new CodeLike())()", 7);
 }
 
-UNINITIALIZED_TEST(SingleThreadedDefaultPlatform) {
-  v8::V8::SetFlagsFromString("--single-threaded");
-  auto old_platform = i::V8::GetCurrentPlatform();
-  std::unique_ptr<v8::Platform> new_platform(
-      v8::platform::NewSingleThreadedDefaultPlatform());
-  i::V8::SetPlatformForTesting(new_platform.get());
-  v8::Isolate::CreateParams create_params;
-  create_params.array_buffer_allocator = CcTest::array_buffer_allocator();
-  v8::Isolate* isolate = v8::Isolate::New(create_params);
-  isolate->Enter();
-  i::Isolate* i_isolate = reinterpret_cast<i::Isolate*>(isolate);
-  {
-    i::HandleScope scope(i_isolate);
-    v8::Local<Context> env = Context::New(isolate);
-    env->Enter();
-
-    CompileRunChecked(isolate,
-                      "function f() {"
-                      "  for (let i = 0; i < 10; i++)"
-                      "    (new Array(10)).fill(0);"
-                      "  return 0;"
-                      "}"
-                      "f();");
-    env->Exit();
-  }
-  CcTest::CollectGarbage(i::NEW_SPACE, i_isolate);
-  CcTest::CollectAllAvailableGarbage(i_isolate);
-  isolate->Exit();
-  isolate->Dispose();
-  i::V8::SetPlatformForTesting(old_platform);
-}
-
 THREADED_TEST(MicrotaskQueueOfContext) {
   auto microtask_queue = v8::MicrotaskQueue::New(CcTest::isolate());
   v8::HandleScope scope(CcTest::isolate());

test/unittests/BUILD.gn

@@ -360,6 +360,7 @@ v8_source_set("unittests_sources") {
     "libplatform/default-job-unittest.cc",
     "libplatform/default-platform-unittest.cc",
     "libplatform/default-worker-threads-task-runner-unittest.cc",
+    "libplatform/single-threaded-default-platform-unittest.cc",
     "libplatform/task-queue-unittest.cc",
     "libplatform/worker-thread-unittest.cc",
     "logging/counters-unittest.cc",

test/unittests/libplatform/single-threaded-default-platform-unittest.cc

+// Copyright 2022 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "include/v8-platform.h"
+#include "test/unittests/test-utils.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace v8 {
+
+template <typename TMixin>
+class WithSingleThreadedDefaultPlatformMixin : public TMixin {
+ public:
+  WithSingleThreadedDefaultPlatformMixin() {
+    platform_ = v8::platform::NewSingleThreadedDefaultPlatform();
+    CHECK_NOT_NULL(platform_.get());
+    v8::V8::InitializePlatform(platform_.get());
+#ifdef V8_SANDBOX
+    CHECK(v8::V8::InitializeSandbox());
+#endif  // V8_SANDBOX
+    v8::V8::Initialize();
+  }
+
+  ~WithSingleThreadedDefaultPlatformMixin() override {
+    CHECK_NOT_NULL(platform_.get());
+    v8::V8::Dispose();
+    v8::V8::DisposePlatform();
+  }
+
+  v8::Platform* platform() const { return platform_.get(); }
+
+ private:
+  std::unique_ptr<v8::Platform> platform_;
+};
+
+class SingleThreadedDefaultPlatformTest
+    : public WithContextMixin<                             //
+          WithIsolateScopeMixin<                           //
+              WithIsolateMixin<                            //
+                  WithSingleThreadedDefaultPlatformMixin<  //
+                      ::testing::Test>>>> {
+ public:
+  static void SetUpTestSuite() {
+    CHECK_NULL(save_flags_);
+    save_flags_ = new i::SaveFlags();
+    v8::V8::SetFlagsFromString("--single-threaded");
+    WithContextMixin::SetUpTestSuite();
+  }
+
+  static void TearDownTestSuite() {
+    WithContextMixin::TearDownTestSuite();
+    CHECK_NOT_NULL(save_flags_);
+    delete save_flags_;
+    save_flags_ = nullptr;
+  }
+
+ private:
+  static i::SaveFlags* save_flags_;
+};
+
+// static
+i::SaveFlags* SingleThreadedDefaultPlatformTest::save_flags_;
+
+TEST_F(SingleThreadedDefaultPlatformTest, SingleThreadedDefaultPlatform) {
+  RunJS(
+      "function f() {"
+      "  for (let i = 0; i < 10; i++)"
+      "    (new Array(10)).fill(0);"
+      "  return 0;"
+      "}"
+      "f();");
+}
+
+}  // namespace v8