Example of testing the index handler for simple server

createSimpleServerIndexHandlerTest.go

func TestIndex(t *testing.T) {
	req, err := http.NewRequest(http.MethodGet, "/", nil)
	if err != nil {
		t.Fatalf("TestIndex: couldn't create HTTP GET request: %v", err)
	}

	rec := httptest.NewRecorder()

	index().ServeHTTP(rec, req)

	res := rec.Result()
	defer func() {
		err := res.Body.Close()
		if err != nil {
			t.Fatalf("TestIndex: couldn't close response body: %v", err)
		}
	}()

	if res.StatusCode != http.StatusOK {
		t.Errorf("TestIndex: got status code %v, but want: %v", res.StatusCode, http.StatusOK)
	}

	body, err := ioutil.ReadAll(res.Body)
	if err != nil {
		t.Fatalf("TestIndex: could not read response body: %v", err)
	}

	if len(string(body)) == 0 {
		t.Errorf("TestIndex: unexpected empty response body")
	}
}