Unit test that DnsSocketPool copies RandIntCallback

net/dns/dns_socket_pool_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 "net/dns/dns_socket_pool.h"
+
+#include "base/bind.h"
+#include "base/callback.h"
+#include "base/memory/weak_ptr.h"
+#include "net/base/rand_callback.h"
+#include "net/socket/client_socket_factory.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace net {
+namespace {
+
+class DummyObject {
+ public:
+  DummyObject() : weak_factory_(this) {}
+
+  base::WeakPtr<DummyObject> GetWeakPtr() { return weak_factory_.GetWeakPtr(); }
+
+  bool HasWeakPtrs() const { return weak_factory_.HasWeakPtrs(); }
+
+ private:
+  base::WeakPtrFactory<DummyObject> weak_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(DummyObject);
+};
+
+class DummyRandIntCallback {
+ public:
+  DummyRandIntCallback() {}
+
+  RandIntCallback MakeCallback() {
+    return base::Bind(&DummyRandIntCallback::GetRandInt, dummy_.GetWeakPtr());
+  }
+
+  bool HasRefs() const { return dummy_.HasWeakPtrs(); }
+
+ private:
+  static int GetRandInt(base::WeakPtr<DummyObject> dummy, int from, int to) {
+    // Chosen by fair dice roll. Guaranteed to be random.
+    return 4;
+  }
+
+  DummyObject dummy_;
+
+  DISALLOW_COPY_AND_ASSIGN(DummyRandIntCallback);
+};
+
+// Before the below tests rely upon it, make sure that DummyRandIntCallback

[mmenke, 2017/01/30 20:15:29]

nit:  Before -> Because?  Tests aren't guaranteed to run in order on the bots, I
believe?

[Julia Tuttle, 2017/01/30 20:42:42]

Done.

+// can reliably tell whether there are other refs to the callback it returns.
+
+// A const reference to the callback shouldn't keep the callback referenced.
+TEST(DummyRandIntCallbackTest, Referenced) {
+  DummyRandIntCallback dummy;
+
+  RandIntCallback original = dummy.MakeCallback();
+  EXPECT_FALSE(dummy.HasRefs());
+  const RandIntCallback& reference = original;
+  EXPECT_TRUE(dummy.HasRefs());
+
+  EXPECT_EQ(4, reference.Run(0, 6));
+
+  original.Reset();
+  EXPECT_FALSE(dummy.HasRefs());
+}
+
+// A copy of the callback should keep the callback referenced.
+TEST(DummyRandIntCallbackTest, Copied) {
+  DummyRandIntCallback dummy;
+
+  RandIntCallback original = dummy.MakeCallback();
+  EXPECT_FALSE(dummy.HasRefs());
+  RandIntCallback copy = original;
+  EXPECT_TRUE(dummy.HasRefs());
+
+  EXPECT_EQ(4, copy.Run(0, 6));
+
+  original.Reset();
+  EXPECT_TRUE(dummy.HasRefs());
+}
+
+class DnsSocketPoolTest : public ::testing::Test {
+ protected:
+  DummyRandIntCallback dummy_;
+  std::unique_ptr<DnsSocketPool> pool_;
+};
+
+// Make sure that the DnsSocketPools returned by CreateDefault and CreateNull
+// both retain (by copying the RandIntCallback object, instead of taking a
+// reference) the RandIntCallback used for creating sockets.
+
+TEST_F(DnsSocketPoolTest, DefaultCopiesCallback) {
+  pool_ = DnsSocketPool::CreateDefault(ClientSocketFactory::GetDefaultFactory(),
+                                       dummy_.MakeCallback());
+  EXPECT_TRUE(dummy_.HasRefs());
+}
+
+TEST_F(DnsSocketPoolTest, NullCopiesCallback) {
+  pool_ = DnsSocketPool::CreateNull(ClientSocketFactory::GetDefaultFactory(),
+                                    dummy_.MakeCallback());
+  EXPECT_TRUE(dummy_.HasRefs());
+}
+
+}  // namespace
+}  // namespace net