`httptest` パッケージを使用して Go で HTTP 呼び出しを効果的にテストするにはどうすればよいですか?

func TestHeader3D(t *testing.T) {
    resp := httptest.NewRecorder()
    // ... setup the request with headers and parameters ...
    http.DefaultServeMux.ServeHTTP(resp, req)
    // ... assert the response body and content type ...
}

func TestIt(t *testing.T) {
    ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        // ... your handler setup and response ...
    }))
    defer ts.Close()
    // ... setup your requests and make assertions based on the responses ...
}

func TestRetrieveTweets(t *testing.T) {
    ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        // Set up your mock response for the Twitter API ...
    }))
    defer ts.Close()
    twitterUrl = ts.URL
    c := make(chan *twitterResult)
    go retrieveTweets(c)
    // ... assert the results you receive in the `c` channel ...
}