How to test uber dig application Golang - go

Question

I recently wanted to try out dependency injection in golang and I picked up Uber dig container everything working well but I am not sure how to test my code.
My dig container
func buildContainer() *dig.Container {
container := dig.New()
_ = container.Provide(config.GetInstance)
_ = container.Provide(database.GetInstance)
_ = container.Provide(evaluation.NewEvaluator)
_ = container.Provide(repository.NewExperimentRepository)
return container
}
My Dao
type ExperimentDao interface {
// Create experiment
Create(experiment *models.Experiment) error
// Update experiment
Update(experiment *models.Experiment) error
// FindByID find experiment by id
FindByID(id string) (*models.Experiment, error)
//FindAll find all the questions
FindAll(filter bson.M, page int, limit int) (*models.ExperimentPagination, error)
}
My Repository that implements the doa interface
type ExperimentRepository struct {
DB *database.DB
}
// NewExperimentRepository returns new ExperimentDao
func NewExperimentRepository(db *database.DB) interfaces.ExperimentDao {
return &ExperimentRepository{DB: db}
}
func (expRepo *ExperimentRepository) Create(experiment *models.Experiment) error {
//repository code to insert in DB
}
// rest of the implemented func(s)
Here is my handler where I use the injected Repository to insert the data
func CreateExperiment(res http.ResponseWriter, req *http.Request) {
experiment := models.Experiment{}
err := json.NewDecoder(req.Body).Decode(&experiment)
if err != nil {
logrus.Error("Create Experiment Error parsing payload : ", err)
utils.RespondError(res, err, 400)
return
}
ValErr := ValidateExpt(experiment, "create")
if ValErr != "" {
logrus.Error("Create Experiment Error : ", ValErr)
utils.Respond(res, ValErr, 400)
return
}
di := container.GetInstance()
err = di.Invoke(func(dao interfaces.ExperimentDao) {
err := dao.Create(&experiment)
if err != nil {
utils.RespondError(res, err, http.StatusInternalServerError)
return
}
utils.Respond(res, "experiment created successfully", http.StatusOK)
})
if err != nil {
logrus.Error("Insert Experiment Error : ", err)
utils.RespondError(res, err, 400)
}
}
// Di builder
func GetInstance() *dig.Container {
once.Do(func() {
container = buildContainer()
})
return container
}
Now as the code is working fine as expected so I hope the approach is correct as per my knowledge but now I am unable to figure out how to write the test to test this code I can write few validations for experiment model but not for repository, dao or the di container.
Can you guys help where should I look or what am I missing.
Thanks.

Answer 1

I would suggest you to write a function, that will receive all dependencies as parameters and will return the HTTP handler, like this:
func NewCreateExperimentHandler(c *dig.Container) http.HandlerFunc {
return func (res http.ResponseWriter, req *http.Request) {
// the current CreateExperiment() implementation
}
}
This will allow you to mock your container inside the tests.