How to mock http.Client Do method

Question

I'm trying to find a solution to write test and mock HTTP response. In my function where I accept interface:

type HttpClient interface {
    Do(req *http.Request) (*http.Response, error)
}

I makes http get request with base auth

func GetOverview(client HttpClient, overview *Overview) (*Overview, error) {

    request, err := http.NewRequest("GET", fmt.Sprintf("%s:%s/api/overview", overview.Config.Url, overview.Config.Port), nil)
    if (err != nil) {
        log.Println(err)
    }
    request.SetBasicAuth(overview.Config.User, overview.Config.Password)
    resp, err := client.Do(request)

How can I mock this HttpClient? I'm looking for mock library, for instance: https://github.com/h2non/gock but there is only mock for Get and Post

Maybe I should do it in a different way. I'll be grateful for advice

Answer 1

Any struct with a method matching the signature you have in your interface will implement the interface. For example, you could create a struct ClientMock

type ClientMock struct {
}

with the method

func (c *ClientMock) Do(req *http.Request) (*http.Response, error) {
    return &http.Response{}, nil
}

You could then inject this ClientMock struct into your GetOverview func. Here's an example in the Go Playground.