Fix leak of sequenced worker pool in unit tests when service_ is replaced.

net/ssl/server_bound_cert_service_unittest.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 "net/ssl/server_bound_cert_service.h"
 
 #include <string>
 #include <vector>
 
 #include "base/bind.h"
@@ skipping 518 matching lines @@
 
   mock_store->CallGetServerBoundCertCallbackWithResult(
       ERR_FILE_NOT_FOUND, base::Time(), std::string(), std::string());
 
   error = callback.WaitForResult();
   EXPECT_EQ(OK, error);
   EXPECT_EQ(1, service_->cert_count());
   EXPECT_FALSE(private_key_info.empty());
   EXPECT_FALSE(der_cert.empty());
   EXPECT_FALSE(request_handle.is_active());
-}
+
+  // Wait for any posted ServerBoundCertServiceWorkers to finish, in order to
+  // ensure that the workers are cleared by the time service_'s destructor is
+  // called. This prevents a leak of the SequencedWorkerPool, which by default
+  // continues on shutdown.  (By calling
+  // CallGetServerBoundCertCallbackWithResult, callbacks are called directly,
+  // short-circuiting ServerBoundCertService's usual bookkeeping, so existing
+  // tasks must be both cleared and waited for to ensure proper memory freeing.)
+  sequenced_worker_pool_->FlushForTesting();

[Ryan Sleevi, 2013/08/09 00:45:10]

I can't help but keep reading this comment and code and not understanding what's
expected/correct.

It seems like your Mock is broken/violating expectations. Should you be
PostTasking from CallGetServerBoundCertCallbackWithResult to match the semantics
of the ServerBoundCertStore, so that you then use FlushForTesting &
RunUntilIdle?

This definitely seems to match the interface you're mocking, since you're
returning ERR_IO_PENDING (which we always handle via PostTask yielding)

[juanlang, 2013/08/09 04:48:52]

Yeah, that big comment should have been a clue to me that I still hadn't
understood entirely. These tests are similar to the other tests. I repeat the
pattern of the other tests here.
I thought so too, but upon further reading I believe my Mock is behaving
substantially like the real store.

[juanlang, 2013/08/09 16:25:28]

Yep, PostTask is the right thing here. Thanks. I don't need to FlushForTesting
and RunUntilIdle when I use it, either, because by PostTasking and then calling
callback.WaitForResult, the workers correctly terminate already.

In other words, done.

+  base::MessageLoop::current()->RunUntilIdle(); }
 
 TEST_F(ServerBoundCertServiceTest, AsyncStoreGetOneCertInStore) {
   MockServerBoundCertStoreWithAsyncGet* mock_store =
       new MockServerBoundCertStoreWithAsyncGet();
   service_ = scoped_ptr<ServerBoundCertService>(
       new ServerBoundCertService(mock_store, sequenced_worker_pool_));
 
   std::string host("encrypted.google.com");
 
   int error;
   TestCompletionCallback callback;
   ServerBoundCertService::RequestHandle request_handle;
 
   // Asynchronous completion with a cert in the store.
   std::string private_key_info, der_cert;
   EXPECT_EQ(0, service_->cert_count());
   error = service_->GetDomainBoundCert(
       host, &private_key_info, &der_cert, callback.callback(), &request_handle);
   EXPECT_EQ(ERR_IO_PENDING, error);
   EXPECT_TRUE(request_handle.is_active());
 
   mock_store->CallGetServerBoundCertCallbackWithResult(
       OK, base::Time(), "ab", "cd");
-
   error = callback.WaitForResult();
   EXPECT_EQ(OK, error);
   EXPECT_EQ(1, service_->cert_count());
   EXPECT_EQ(1u, service_->requests());
   EXPECT_EQ(1u, service_->cert_store_hits());
   // Because the cert was found in the store, no new workers should have been
   // created.
   EXPECT_EQ(0u, service_->workers_created());
   EXPECT_STREQ("ab", private_key_info.c_str());
   EXPECT_STREQ("cd", der_cert.c_str());
   EXPECT_FALSE(request_handle.is_active());
+
+  // Wait for any posted ServerBoundCertServiceWorkers to finish, in order to
+  // ensure that the workers are cleared by the time service_'s destructor is
+  // called. This prevents a leak of the SequencedWorkerPool, which by default
+  // continues on shutdown.  (By calling
+  // CallGetServerBoundCertCallbackWithResult, callbacks are called directly,
+  // short-circuiting ServerBoundCertService's usual bookkeeping, so existing
+  // tasks must be both cleared and waited for to ensure proper memory freeing.)
+  sequenced_worker_pool_->FlushForTesting();
+  base::MessageLoop::current()->RunUntilIdle(); }
 }
 
 #endif  // !defined(USE_OPENSSL)
 
 }  // namespace
 
 }  // namespace net