Testing Threads

initial_implementation.cc

void MyClass::FetchMagicNumber(std::function<void(int)> callback) {
  std::weak_ptr<MyClass> weak_this = shared_from_this();
  auto fetch_results = [weak_this] {
    auto shared_this = weak_this.lock();
    if (!shared_this) return -1;
    
    return shared_this->requester_->DoLongWebRequest();
  };
  
  system::Runtime::net_io.Post<int>(fetch_results, callback, system::Runtime::ui());
}

injected_implementation.cc

void MyClass::FetchMagicNumber(std::function<void(int)> callback, 
                         const system::JobRunner* request_thread, 
                         const system::JobRunner* callback_thread) {
  std::weak_ptr<MyClass> weak_this = shared_from_this();
  auto fetch_results = [weak_this] {
    auto shared_this = weak_this.lock();
    if (!shared_this) return -1;
    
    return shared_this->requester_->DoLongWebRequest();
  };
  
  request_thread.Post<Stuff>(fetch_results, callback, callback_thread);
}

test.cc

TEST(MyClassTest, CallsCallbackWithResult) {
  constexpr int kAnswerToLifeTheUniverseAndEverything = 42;
  constexpr int kErrorCode = -1;
  
  MockRequester requester;
  ON_CALL(requester, DoLongWebRequest()).WillByDefaultReturn(kAnswerToLifeTheUniverseAndEverything);
  std::shared_ptr<MyClass> instance = MyClass::Create(&requester);
  
  MockFunction<void(std::unique_ptr<Stuff>)> callback;
  EXPECT_CALL(callback, Call(kAnswerToLifeTheUniverseAndEverything));
  
  system::NonBlockingJobRunner request_thread;
  system::NonBlockingJobRunner callback_thread;
  
  instance.FetchStuff(callback, &request_thread, &callback_thread);
  
  request_thread.ExecuteAll();
  callback_thread.ExecuteAll();
}

TEST(MyClassTest, CallsCallbackWithErrorCode) {
  constexpr int kAnswerToLifeTheUniverseAndEverything = 42;
  constexpr int kErrorCode = -1;
  
  MockRequester requester;
  ON_CALL(requester, DoLongWebRequest()).WillByDefaultReturn(kAnswerToLifeTheUniverseAndEverything);
  std::shared_ptr<MyClass> instance = MyClass::Create(&requester);
  
  MockFunction<void(std::unique_ptr<Stuff>)> callback;
  EXPECT_CALL(callback, Call(kErrorCode));
  
  system::NonBlockingJobRunner request_thread;
  system::NonBlockingJobRunner callback_thread;
  
  instance.FetchStuff(callback, &request_thread, &callback_thread);
  
  instance.reset();
  
  request_thread.ExecuteAll();
  callback_thread.ExecuteAll();
}