[Doodle] Introduce a DoodleService

components/doodle/doodle_service_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 "components/doodle/doodle_service.h"
+
+#include <memory>
+#include <utility>
+#include <vector>
+
+#include "base/bind.h"
+#include "base/memory/ptr_util.h"
+#include "testing/gmock/include/gmock/gmock.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+using testing::Eq;
+using testing::Ne;
+
+namespace doodle {
+
+namespace {
+
+class FakeDoodleFetcher : public DoodleFetcher {
+ public:
+  FakeDoodleFetcher() = default;
+  ~FakeDoodleFetcher() override = default;
+
+  void FetchDoodle(FinishedCallback callback) override {
+    callbacks_.push_back(std::move(callback));
+  }
+
+  size_t num_pending_callbacks() const { return callbacks_.size(); }
+
+  void ServeAllCallbacks(DoodleState state,
+                         const base::Optional<DoodleConfig>& config) {
+    for (auto& callback : callbacks_) {
+      std::move(callback).Run(state, config);
+    }
+    callbacks_.clear();
+  }
+
+ private:
+  std::vector<FinishedCallback> callbacks_;
+};
+
+class MockDoodleObserver : public DoodleService::Observer {
+ public:
+  MOCK_METHOD1(OnDoodleConfigUpdated,
+               void(const base::Optional<DoodleConfig>&));
+};
+
+}  // namespace
+
+class DoodleServiceTest : public testing::Test {
+ public:
+  DoodleServiceTest() : fetcher_(nullptr) {
+    auto fetcher = base::MakeUnique<FakeDoodleFetcher>();
+    fetcher_ = fetcher.get();
+    service_ = base::MakeUnique<DoodleService>(std::move(fetcher));
+  }
+
+  DoodleService* service() { return service_.get(); }
+  FakeDoodleFetcher* fetcher() { return fetcher_; }
+
+ private:
+  std::unique_ptr<DoodleService> service_;
+  FakeDoodleFetcher* fetcher_;
+};
+
+TEST_F(DoodleServiceTest, CallsObserverImmediately) {
+  MockDoodleObserver observer;
+
+  // When an observer is added, it should immediately receive the current doodle
+  // config (which in this case is empty).
+  EXPECT_CALL(observer, OnDoodleConfigUpdated(Eq(base::nullopt)));
+  service()->AddObserver(&observer);

[fhorschig, 2017/02/24 15:33:14]

If you remove the "immediate call side effect"; declaring, adding and
removing the observer can happen in ctor/dtor and expectations could
still happen here.

(You seem to use it very often but if you consider it an important part
of the setup, feel free to ignore this comment).

[Marc Treib, 2017/02/24 16:18:51]

Well, so far there are only two tests, so not all that often :D

I'll see about moving this into the Test class once there are more tests (and
once we've decided on an API). But I expect that some tests will have multiple
observers, while some others might not need any, so maybe it's better to leave
it explicitly in the test. We'll see.

+
+  // Remove the observer before the service gets destroyed.
+  service()->RemoveObserver(&observer);
+}
+
+TEST_F(DoodleServiceTest, CallsObserverOnReceivingConfig) {
+  MockDoodleObserver observer;
+
+  // When an observer is added, it should immediately receive the current doodle
+  // config (which at this point is empty).
+  EXPECT_CALL(observer, OnDoodleConfigUpdated(Eq(base::nullopt)));
+  service()->AddObserver(&observer);
+
+  // Request a refresh of the doodle config.
+  service()->Refresh();
+  // The request should have arrived at the fetcher.
+  EXPECT_THAT(fetcher()->num_pending_callbacks(), Eq(1u));
+
+  // Serve it (with an arbitrary config). The observer should get notified.
+  DoodleConfig config;
+  config.doodle_type = DoodleType::SLIDESHOW;
+  EXPECT_CALL(observer, OnDoodleConfigUpdated(Ne(base::nullopt)));
+  // TODO: also check that the config matches?
+  fetcher()->ServeAllCallbacks(DoodleState::AVAILABLE, config);
+
+  // Remove the observer before the service gets destroyed.
+  service()->RemoveObserver(&observer);
+}
+
+}  // namespace doodle