usecase_test.go

type tweetUsecaseSuite struct {
	// we need this to use the suite functionalities from testify
	suite.Suite
	// the generated mocked version of our repository
	repository *mocks.TweetRepository
	// the functionalities we want to test
	usecase TweetUsecase
}

func (suite *tweetUsecaseSuite) SetupTest() {
	// instantiate the mocked version of repository
	repository := new(mocks.TweetRepository)
	// inject the repository to usecase, since usecase needs repository to work
	usecase := InitializeTweetUsecase(repository)

	// assign them as the suite properties
	suite.repository = repository
	suite.usecase = usecase
}

func (suite *tweetUsecaseSuite) TestCreateTweet_Positive() {
	// create an example of tweet that will be used in usecase's CreateTweet method
	tweet := entities.Tweet{
		Username: "username",
		Text: "text",
	}
	
	// specify that inside usecase's CreateTweet method
	// repository's CreateTweet method will be called
	suite.repository.On("CreateTweet", &tweet).Return(nil)

	// the real operation we need to test
	err := suite.usecase.CreateTweet(&tweet)
	
	// assertions to make sure our operation does the right thing
	suite.Nil(err, "err is a nil pointer so no error in this process")
	suite.repository.AssertExpectations(suite.T())
}