apourchet/fakenet

FakeNet

A Golang HTTP client that can dropped-in for *http.Client or any interface that *http.Client satisfies. It gives testing flexibility through the use of request interceptors, bypassing the network stack when certain user-described conditions are met. This package is useful in the context of unit tests, where we do not want to depend on the network and need consistent pre-determined responses to requests.

Example

The following example illustrates how one could implement a website status checker package. In a production/live environment, we want the requests to be sent through to the network; but in unit tests we want to setup pre-determined responses to the GET requests that it issues.

// website_checker.go
package checker

type Checker struct {
	NetworkClient HTTPClient
}

type HTTPClient interface {
	Get(url string) (*http.Response, error)
}

func New(client HTTPClient) Checker {
	return Checker{
		NetworkClient: client,
	}
}

func (checker Checker) IsWebsiteUp() bool {
	resp, err := checker.NetworkClient.Get("http://example.org")
	return err == nil && resp.StatusCode == 200
}

And now for the unit tests:

// website_checker_test.go
package checker_test

import "testing"

func TestErrorResponse(t *testing.T) {
	client := fakenet.New()
	catchall := fakenet.CatchAllInterceptor(nil, errors.New("Fell through to the catch all"))
	client.Intercept(catchall)
    
	checker := checker.New(client)
	if checker.IsWebsiteUp() {
		t.Fail("Checker should say website is down if we receive an error in the request")
	}
}

func TestBadStatusCode(t *testing.T) {
	client := fakenet.New()
	client.CatchAll(http.StatusInternalServerError, "Failed to load website.")
    
	checker := checker.New(client)
	if checker.IsWebsiteUp() {
		t.Fail("Checker should say website is down if we receive non-200 status code")
	}
}

func TestWebsiteIsLive(t *testing.T) {
	client := fakenet.New()	
	client.CatchAll(http.StatusOK, "Website is live!")
    
	checker := checker.New(client)
	if !checker.IsWebsiteUp() {
		t.Fail("Checker should say website is up if the status code is 200")
	}
}