2018-11-02 22:47
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So currently I have a http handler that looks like:

type App struct {

func (a *App) someHandler(w http.ResponseWriter, r *http.Request) {
        var api = slack.New("TOKEN")
        users = api.GetUsers()

I want to create an interface for this slack.New("...") call so that in my tests the api doesn't make network requests to slack.

How can I mock this New call?

The call New("TOKEN") returns a *Client, see the link below:

func New(token string, options ...Option) *Client {
    s := &Client{
        token:      token,
        httpclient: &http.Client{},
        log:        log.New(os.Stderr, "nlopes/slack", log.LstdFlags|log.Lshortfile),

    for _, opt := range options {

    return s

I haven't used interfaces that much so not sure if this can't be put in a interface since the call to New is like a constructor?

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1条回答 默认 最新

  • dongxing9219 2018-11-03 06:40

    You can't mock the slack.New call itself, instead you have to create a mock that behaves like this api object. To do this put the api onto the App struct but as an interface:

    type SlackClient interface {
        GetUsers() []string
    type App struct {
        api SlackClient
    func (a *App) someHandler(w http.ResponseWriter, r *http.Request) { 
        users = a.api.GetUsers() 

    You then have to move the call to slack.New into whatever constructs the App (for instance your main function or a NewApp constructor function):

    app = App{api: slack.New("TOKEN")}

    The *Client this returns has a GetUsers method on it so will match the interface we have defined.

    The test then does something similar with a mock:

    type mockSlackClient struct {
    func (m *mockSlackClient) GetUsers() []string {
        return nil
    func TestSomeHandler(t *testing.T) {
        appToTest := App{api: &mockSlackClient{})
        appToTest.someHandler(httptest.NewRecorder(), nil)

    Again as the *mockSlackClient has a GetUsers method on it it will satisfy the interface so you will be able to use it on the App.

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