test_func.go

func TestRouter(t *testing.T) {
	// Instantiate the router using the constructor function that
	// we defined previously
	r := newRouter()

	// Create a new server using the "httptest" libraries `NewServer` method
	// Documentation : https://golang.org/pkg/net/http/httptest/#NewServer
	mockServer := httptest.NewServer(r)

	// The mock server we created runs a server and exposes its location in the
	// URL attribute
	// We make a GET request to the "hello" route we defined in the router
	resp, err := http.Get(mockServer.URL + "/hello")

	// Handle any unexpected error
	if err != nil {
		t.Fatal(err)
	}

	// We want our status to be 200 (ok)
	if resp.StatusCode != http.StatusOK {
		t.Errorf("Status should be ok, got %d", resp.StatusCode)
	}

	// In the next few lines, the response body is read, and converted to a string
	defer resp.Body.Close()
	// read the body into a bunch of bytes (b)
	b, err := ioutil.ReadAll(resp.Body)
	if err != nil {
		t.Fatal(err)
	}
	// convert the bytes to a string
	respString := string(b)
	expected := "Hello World!"

	// We want our response to match the one defined in our handler.
	// If it does happen to be "Hello world!", then it confirms, that the
	// route is correct
	if respString != expected {
		t.Errorf("Response should be %s, got %s", expected, respString)
	}

}