UseCase { public GitHubService getGitHubService() { return gitHubService; } UseCase(GitHubService gitHubService, ThreadExecutor threadExecutor,
      PostExecutionThread postExecutionThread); GitHubService getGitHubService(); Subscription getSubscription(); abstract Observable buildUseCase(String query); @SuppressWarnings("unchecked") void execute(Subscriber useCaseSubscriber, String query); void unsubscribe();  }
@Test public void getGitHubServiceShouldNotReturnNull() throws Exception { GitHubService gitHubService = useCase.getGitHubService(); assertNotNull(gitHubService); }