Destroy all Singletons and LazyInstances between each test.

base/test/test_suite.cc

 // Copyright (c) 2012 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/test/test_suite.h"
 
 #include "base/at_exit.h"
 #include "base/base_paths.h"
 #include "base/base_switches.h"
 #include "base/command_line.h"
@@ skipping 58 matching lines @@
   virtual void OnTestEnd(const testing::TestInfo& test_info) OVERRIDE {
     *CommandLine::ForCurrentProcess() = old_command_line_;
   }
 
  private:
   CommandLine old_command_line_;
 
   DISALLOW_COPY_AND_ASSIGN(TestClientInitializer);
 };
 
+// This class forces the destruction of all Singletons and LazyInstances
+// between tests. Deleting singletons between each test prevents state from
+// being shared amongst tests, which can lead to subtle bugs in tests.
+class SingletonDestructor : public testing::EmptyTestEventListener {
+ public:
+  SingletonDestructor() {}
+  virtual ~SingletonDestructor() {}
+
+  // testing::EmptyTestEventListener:
+  virtual void OnTestStart(
+      const testing::TestInfo& test_info) OVERRIDE {
+    at_exit_manager_.reset(new base::ShadowingAtExitManager);
+  }
+
+  virtual void OnTestEnd(const testing::TestInfo& test_info) OVERRIDE {
+    at_exit_manager_.reset();
+  }
+
+ private:
+  scoped_ptr<base::ShadowingAtExitManager> at_exit_manager_;
+
+  DISALLOW_COPY_AND_ASSIGN(SingletonDestructor);
+};
+
 }  // namespace
 
 TestSuite::TestSuite(int argc, char** argv) : initialized_command_line_(false) {
   PreInitialize(argc, argv, true);
 }
 
 TestSuite::TestSuite(int argc, char** argv, bool create_at_exit_manager)
     : initialized_command_line_(false) {
   PreInitialize(argc, argv, create_at_exit_manager);
 }
@@ skipping 156 matching lines @@
     SuppressErrorDialogs();
     base::debug::SetSuppressDebugUI(true);
     logging::SetLogAssertHandler(UnitTestAssertHandler);
   }
 
   icu_util::Initialize();
 
   CatchMaybeTests();
   ResetCommandLine();
 
+  // Add a listener to destroy all Singletons and LazyInstances between each
+  // test. See SingletonDestructor for more information.
+  testing::TestEventListeners& listeners =
+      testing::UnitTest::GetInstance()->listeners();
+  listeners.Append(new SingletonDestructor);
+
   TestTimeouts::Initialize();
 }
 
 void TestSuite::Shutdown() {
 }