Unit test http request retries using httptest

php editor Baicao introduces you to a unit testing tool called "httptest", which can help developers test when retrying http requests. This tool can not only simulate various http requests, but also automatically retry requests to ensure the stability and reliability of the code. Using the httptest tool, developers can easily unit test http requests, and can easily retry requests to deal with network instability or other abnormal situations. The use of this tool can greatly improve development efficiency and reduce the possibility of errors. It is a tool worth trying for every PHP developer.

Question content

I'm trying to write unit tests for a component called HttpRequest that wraps HTTP requests and handles response unmarshalling. Recently, I added a feature to this component that allows it to retry HTTP requests if it encounters a "connection refused" error on the first try.

To use the HttpRequest component, I call it once: user, err := HttpRequest[User](config). The config parameter contains all the necessary information to perform the request, such as URL, method, timeout, number of retries, and request body. It also unmarshals the response body into an instance of the specified type (User in this case)

The problem arises when I try to test a scenario where the initial request fails with a "Connection refused" error but the second attempt succeeds. The retry happens inside the component, so I only make one call to the component.

I found it challenging to create unit tests for this situation because in order for the request to fail with "Connection refused" there doesn't need to be a listener on the port being called. The problem is that when using httptest it always listens on the port when the instance is created, even when using httptest.NewUnstartedServer. Therefore, I will never encounter a "connection refused" error in my client code after creating the httptest instance.

However, I don't know which port it will listen on until I create the httptest instance. httptest always chooses a random port, and there is no way to programmatically specify a port. This means I can't make the HttpRequest call before creating the httptest instance.

Does anyone have any ideas on how to effectively unit test this scenario?

Solution

newunstartedserver Very simple:

func newunstartedserver(handler http.handler) *server {
    return &server{
        listener: newlocallistener(),
        config:   &http.server{handler: handler},
    }
}

If you choose a port that suits you, you can do this:

func mynewunstartedserver(port int, handler http.handler) *httptest.server {
    addr := fmt.sprintf("127.0.0.1:%d", port)
    l, err := net.listen("tcp", addr)
    if err != nil {
        addr = fmt.sprintf("[::1]::%d", port)
        if l, err = net.listen("tcp6", addr); err != nil {
            panic(fmt.sprintf("httptest: failed to listen on a port: %v", err))
        }
    }
    return &httptest.server{
        listener: l,
        config:   &http.server{handler: handler},
    }
}

The code to create the listener is modified from httptest.newlocallistener.

Another option is to implement the http.roundtripper interface and create a http.client using this roundtripper. The following is an example http/client_test.go copied from net/:

type recordingTransport struct {
    req *Request
}

func (t *recordingTransport) RoundTrip(req *Request) (resp *Response, err error) {
    t.req = req
    return nil, errors.New("dummy impl")
}

func TestGetRequestFormat(t *testing.T) {
    setParallel(t)
    defer afterTest(t)
    tr := &recordingTransport{}
    client := &Client{Transport: tr}
    url := "http://dummy.faketld/"
    client.Get(url) // Note: doesn't hit network
    if tr.req.Method != "GET" {
        t.Errorf("expected method %q; got %q", "GET", tr.req.Method)
    }
    if tr.req.URL.String() != url {
        t.Errorf("expected URL %q; got %q", url, tr.req.URL.String())
    }
    if tr.req.Header == nil {
        t.Errorf("expected non-nil request Header")
    }
}

The above is the detailed content of Unit test http request retries using httptest. For more information, please follow other related articles on the PHP Chinese website!