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Creating a Test HTTP Server in Go

muaazsaleem

Muaaz Saleem

Posted on January 17, 2021

Creating a Test HTTP Server in Go

httptest.NewServer gives us the ability to spin up a local HTTP Server. This is very useful say, when testing an HTTP client.

Usage

Here's a very basic usage of httptest.NewServer:

server := httptest.NewServer(
        http.HandlerFunc(
            func(w http.ResponseWriter, req *http.Request) {
            _, _ = fmt.Fprint(w, "OK")
        }))
    defer server.Close()
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In the code above, server.URL can be used to connect to the server. For example, we could pass it to the following pingService func to test it.

func pingService(url string) ServiceStatus {
    // TODO: make sure url is actually a valid URL
    res, err := http.Get(url)
    // expecting the HTTP client to err out if the service is down
    if err != nil {
        // TODO: add TestURL to the log
        log.Errorf("[%s], is DOWN", url)
        return ServiceDown
    }
}
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A more complete example

Following is a more complete example of pingService and its tests:

pingService() 

// ServiceStatus indicates the status of a service i.e "UP", "FAILING", "DOWN"
type ServiceStatus string

const (
    ServiceUP      = ServiceStatus("UP")
    ServiceDown    = ServiceStatus("DOWN")
    ServiceFailing = ServiceStatus("FAILING")
)

func pingService(server *http.Server) ServiceStatus {
    // TODO: make sure server.URL is actually a valid URL
    res, err := http.Get(server.URL)
    // expecting the HTTP client to err out if the service is down
    if err != nil {
        // TODO: add TestURL to the log
        log.Errorf("[%s], is DOWN", server.URL)
        return ServiceDown
    }

    if res.StatusCode >= 200 && res.StatusCode <= 500 {
        log.Infof("[%s], is UP", server.URL)
        return ServiceUP
    } else {
        log.Errorf("[%s], is FAILING", server.URL)
        return ServiceFailing
    }
}
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Testing pingService() 

// TestStatusDown tests pinging a non running HTTP service
func TestStatusDown(t *testing.T) {
    ss := pingService(exampleTestService)
    require.Equal(t, ServiceDown, ss)
}

// TestStatusUP tests a running HTTP service
func TestStatusUP(t *testing.T) {
    sv := httptest.NewServer(
        http.HandlerFunc(
            func(w http.ResponseWriter, req *http.Request) {
            _, _ = fmt.Fprint(w, "OK")
        }))
    defer sv.Close()

    ss := pingService(sv)
    require.Equal(t, ServiceUP, ss)
}

// TestStatusFailing tests a failing HTTP service
func TestStatusFailing(t *testing.T) {
    sv := httptest.NewServer(
        http.HandlerFunc(
            func(w http.ResponseWriter, req *http.Request) {
            w.WriteHeader(http.StatusInternalServerError)
        }))
    defer sv.Close()

    ss := pingService(sv)
    require.Equal(t, ServiceFailing, ss)
}
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Further Resources:

💖 💪 🙅 🚩
muaazsaleem
Muaaz Saleem

Posted on January 17, 2021

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