Syasa's 404 test

my_api_test.go

package main

import (
	"io/ioutil"
	"net/http"
	"net/http/httptest"
	"testing"

	"github.com/pkg/errors"
)

var APIRequestNotFound = errors.New("Resource does not exist (404).")
var APIResponseInvalidStatusCode = errors.New("Response was invalid")

// API Class that talks to a third party service
type API struct {
	client *http.Client
}

func NewAPI(client *http.Client) *API {
	api := &API{client: client}
	return api
}

// API method that makes a request to the third party service
func (a *API) MakeRequest(url string) ([]byte, error) {
	resp, err := a.client.Get(url)
	if err != nil {
		return nil, errors.Wrap(err, "Failed to sent request")
	}
	if resp.StatusCode == 404 {
		return nil, APIRequestNotFound
	}
	validResponse := resp.StatusCode >= http.StatusOK && resp.StatusCode < http.StatusMultipleChoices
	if !validResponse {
		return nil, APIResponseInvalidStatusCode
	}

	defer resp.Body.Close()
	body, err := ioutil.ReadAll(resp.Body)
	return body, err
}

// Unit test code

func TestInvalidRequestShouldReturnNotFoundError(t *testing.T) {
	// 1. Create a mock server object that returns 404
	server := httptest.NewServer(http.HandlerFunc(func(rw http.ResponseWriter, req *http.Request) {
		rw.WriteHeader(http.StatusNotFound)
	}))
	defer server.Close()

	// 2. Initilize the object
	sut := NewAPI(server.Client())
	if sut == nil {
		t.Fatalf("Failed to create sut")
	}

	// 3. Make a request
	got, err := sut.MakeRequest(server.URL)

	// 4. Assert if reponse body is not empty
	if len(got) > 0 {
		t.Fatalf("Expected empty body, got body size <%d>", len(got))
	}

	// 5. Assert that the returned error is not RequestNotFound
	if err != APIRequestNotFound {
		t.Fatalf("Expected <%s>, got <%s>", APIRequestNotFound, err)
	}
}