thread: Assert thread quiescence between tests

source/common/common/thread.cc

@@ -31,6 +31,11 @@ struct ThreadIds {
     return main_thread_id_ == id || test_thread_id_ == id;
   }
 
+  bool isMainThreadActive() const {
+    absl::MutexLock lock(&mutex_);
+    return main_thread_use_count_ != 0;
+  }
+
   // Returns a singleton instance of this. The instance is never freed.
   static ThreadIds& get() { MUTABLE_CONSTRUCT_ON_FIRST_USE(ThreadIds); }
 
@@ -101,6 +106,8 @@ struct ThreadIds {
 
 bool MainThread::isMainOrTestThread() { return ThreadIds::get().inMainOrTestThread(); }
 
+bool MainThread::isMainThreadActive() { return ThreadIds::get().isMainThreadActive(); }
+
 TestThread::TestThread() { ThreadIds::get().registerTestThread(); }
 
 TestThread::~TestThread() { ThreadIds::get().releaseTestThread(); }

source/common/common/thread.h

@@ -197,9 +197,14 @@ class MainThread {
   ~MainThread();
 
   /**
-   * Returns whether the current thread is the main thread or test thread.
+   * @return whether the current thread is the main thread or test thread.
    */
   static bool isMainOrTestThread();
+
+  /**
+   * @return whether a MainThread has been instantiated.
+   */
+  static bool isMainThreadActive();
 };
 
 // To improve exception safety in data plane, we plan to forbid the use of raw try in the core code

test/test_listener.cc

@@ -14,6 +14,9 @@ void TestListener::OnTestEnd(const ::testing::TestInfo& test_info) {
                               "]: Active singletons exist. Something is leaking. Consider "
                               "commenting out this assert and letting the heap checker run:\n",
                               active_singletons));
+  RELEASE_ASSERT(!Thread::MainThread::isMainThreadActive(),
+                 absl::StrCat("MainThreadLeak: [", test_info.test_suite_name(), ".",
+                              test_info.name(), "] test exited before main thread shut down"));
 }
 
 } // namespace Envoy