httpmock

Simple Example:

func TestFetchArticles(t *testing.T) {
	httpmock.Activate(&http.DefaultTransport)
	defer httpmock.DeactivateAndReset()

	httpmock.RegisterResponder("GET", "https://api.mybiz.com/articles.json",
		httpmock.NewStringResponder(200, `[{"id": 1, "name": "My Great Article"}]`))

	// do stuff that makes a request to articles.json
}

Advanced Example:

func TestFetchArticles(t *testing.T) {
	httpmock.Activate(&http.DefaultTransport)
	defer httpmock.DeactivateAndReset()

	// our database of articles
	articles := make([]map[string]interface{}, 0)

	// mock to list out the articles
	httpmock.RegisterResponder("GET", "https://api.mybiz.com/articles.json",
		func(req *http.Request) (*http.Response, error) {
			resp, err := httpmock.NewJsonResponse(200, articles)
			if err != nil {
				return httpmock.NewStringResponse(500, ""), nil
			}
			return resp, nil
		},
	)

	// mock to add a new article
	httpmock.RegisterResponder("POST", "https://api.mybiz.com/articles.json",
		func(req *http.Request) (*http.Response, error) {
			article := make(map[string]interface{})
			if err := json.NewDecoder(req.Body).Decode(&article); err != nil {
				return httpmock.NewStringResponse(400, ""), nil
			}

			articles = append(articles, article)

			resp, err := httpmock.NewJsonResponse(200, article)
			if err != nil {
				return httpmock.NewStringResponse(500, ""), nil
			}
			return resp, nil
		},
	)

	// do stuff that adds and checks articles
}