Destroy all Singletons and LazyInstances between each test.

base/test/test_suite.cc

Index: base/test/test_suite.cc
diff --git a/base/test/test_suite.cc b/base/test/test_suite.cc
index 07b9964578a4a860712524443bf977505ef7119c..2d526927c97db097ec95b30ca35bfa7357a3d5db 100644
--- a/base/test/test_suite.cc
+++ b/base/test/test_suite.cc
@@ -76,6 +76,30 @@ class TestClientInitializer : public testing::EmptyTestEventListener {
   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) {
@@ -252,6 +276,12 @@ void TestSuite::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();
 }