Introduce ThreadTaskRunnerHandle::OverrideForTesting and TestMockTimeTaskRunner::ScopedContext.

base/threading/thread_task_runner_handle_unittest.cc

+// Copyright 2017 The Chromium 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 "base/threading/thread_task_runner_handle.h"
+
+#include "base/memory/ref_counted.h"
+#include "base/test/gtest_util.h"
+#include "base/test/test_simple_task_runner.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace base {
+
+TEST(ThreadTaskRunnerHandleTest, Basic) {
+  scoped_refptr<SingleThreadTaskRunner> task_runner(new TestSimpleTaskRunner);
+
+  EXPECT_FALSE(ThreadTaskRunnerHandle::IsSet());
+  {
+    ThreadTaskRunnerHandle ttrh1(task_runner);
+    EXPECT_TRUE(ThreadTaskRunnerHandle::IsSet());
+    EXPECT_EQ(task_runner, ThreadTaskRunnerHandle::Get());
+  }
+  EXPECT_FALSE(ThreadTaskRunnerHandle::IsSet());
+}
+
+TEST(ThreadTaskRunnerHandleTest, DeathOnImplicitOverride) {
+  scoped_refptr<SingleThreadTaskRunner> task_runner(new TestSimpleTaskRunner);
+  scoped_refptr<SingleThreadTaskRunner> overidding_task_runner(
+      new TestSimpleTaskRunner);
+
+  ThreadTaskRunnerHandle ttrh(task_runner);
+  EXPECT_DCHECK_DEATH(
+      { ThreadTaskRunnerHandle overriding_ttrh(overidding_task_runner); });
+}
+
+TEST(ThreadTaskRunnerHandleTest, OverrideForTestingExistingTTRH) {
+  scoped_refptr<SingleThreadTaskRunner> task_runner_1(new TestSimpleTaskRunner);
+  scoped_refptr<SingleThreadTaskRunner> task_runner_2(new TestSimpleTaskRunner);
+  scoped_refptr<SingleThreadTaskRunner> task_runner_3(new TestSimpleTaskRunner);
+  scoped_refptr<SingleThreadTaskRunner> task_runner_4(new TestSimpleTaskRunner);
+
+  EXPECT_FALSE(ThreadTaskRunnerHandle::IsSet());
+  {
+    // TTRH in place prior to override.
+    ThreadTaskRunnerHandle ttrh1(task_runner_1);
+    EXPECT_TRUE(ThreadTaskRunnerHandle::IsSet());
+    EXPECT_EQ(task_runner_1, ThreadTaskRunnerHandle::Get());
+
+    {
+      // Override.
+      ScopedClosureRunner undo_override_2 =
+          ThreadTaskRunnerHandle::OverrideForTesting(task_runner_2);
+      EXPECT_TRUE(ThreadTaskRunnerHandle::IsSet());
+      EXPECT_EQ(task_runner_2, ThreadTaskRunnerHandle::Get());
+
+      {
+        // Nested override.
+        ScopedClosureRunner undo_override_3 =
+            ThreadTaskRunnerHandle::OverrideForTesting(task_runner_3);
+        EXPECT_TRUE(ThreadTaskRunnerHandle::IsSet());
+        EXPECT_EQ(task_runner_3, ThreadTaskRunnerHandle::Get());
+      }
+
+      // Back to single override.
+      EXPECT_TRUE(ThreadTaskRunnerHandle::IsSet());
+      EXPECT_EQ(task_runner_2, ThreadTaskRunnerHandle::Get());
+
+      {
+        // Backup to double override with another TTRH.
+        ScopedClosureRunner undo_override_4 =
+            ThreadTaskRunnerHandle::OverrideForTesting(task_runner_4);
+        EXPECT_TRUE(ThreadTaskRunnerHandle::IsSet());
+        EXPECT_EQ(task_runner_4, ThreadTaskRunnerHandle::Get());
+      }
+    }
+
+    // Back to simple TTRH.
+    EXPECT_TRUE(ThreadTaskRunnerHandle::IsSet());
+    EXPECT_EQ(task_runner_1, ThreadTaskRunnerHandle::Get());
+  }
+  EXPECT_FALSE(ThreadTaskRunnerHandle::IsSet());
+}
+
+TEST(ThreadTaskRunnerHandleTest, OverrideForTestingNoExistingTTRH) {
+  scoped_refptr<SingleThreadTaskRunner> task_runner_1(new TestSimpleTaskRunner);
+  scoped_refptr<SingleThreadTaskRunner> task_runner_2(new TestSimpleTaskRunner);
+
+  EXPECT_FALSE(ThreadTaskRunnerHandle::IsSet());
+  {
+    // Override with no TTRH in place.
+    ScopedClosureRunner undo_override_1 =
+        ThreadTaskRunnerHandle::OverrideForTesting(task_runner_1);
+    EXPECT_TRUE(ThreadTaskRunnerHandle::IsSet());
+    EXPECT_EQ(task_runner_1, ThreadTaskRunnerHandle::Get());
+
+    {
+      // Nested override works the same.
+      ScopedClosureRunner undo_override_2 =
+          ThreadTaskRunnerHandle::OverrideForTesting(task_runner_2);
+      EXPECT_TRUE(ThreadTaskRunnerHandle::IsSet());
+      EXPECT_EQ(task_runner_2, ThreadTaskRunnerHandle::Get());
+    }
+
+    // Back to single override.
+    EXPECT_TRUE(ThreadTaskRunnerHandle::IsSet());
+    EXPECT_EQ(task_runner_1, ThreadTaskRunnerHandle::Get());
+  }
+  EXPECT_FALSE(ThreadTaskRunnerHandle::IsSet());
+}
+
+TEST(ThreadTaskRunnerHandleTest, DeathOnTTRHOverOverride) {
+  scoped_refptr<SingleThreadTaskRunner> task_runner(new TestSimpleTaskRunner);
+  scoped_refptr<SingleThreadTaskRunner> overidding_task_runner(
+      new TestSimpleTaskRunner);
+
+  ScopedClosureRunner undo_override =
+      ThreadTaskRunnerHandle::OverrideForTesting(task_runner);
+  EXPECT_DCHECK_DEATH(
+      { ThreadTaskRunnerHandle overriding_ttrh(overidding_task_runner); });
+}
+
+}  // namespace base