如何在golang中向httptest.server注入URL？

Question

For sentence

resp, err := client.Get(fmt.Sprintf("https://www.xxxxx/day?time=%s", time))

If I want to mock a response to this client.Get() in unit test, I should use httptest.server, but how can I bind the url (https://www.xxxxx/day?time=%s) to the url of httptest.server? so that when I call client.Get() it can return the response I set before. For some reason I cannot mock a client here.

Answer 1

The http.Client is a struct not an interface which makes mocking it difficult as you have seen. An alternative way of mocking it is passing in the external dependencies that a routine needs, so instead of directly using client.Get, you use clientGet - which is a function pointer that was handed into the routine.

From the unit test you can then create :

mockClientGet(c *http.client, url string) (resp *http.Response, err error) {
// add the test code to return what you want it to.
}

Then in your main code use:

resp, err := clientGet(client, fmt.Sprintf("https://www.xxxxx/day?time=%s", time))

When calling the procedure normally, use the function pointer to http.Client.Get, and for your test pass in a pointer to your mock. It's not ideal, but I've not seen a nicer way around mocking non-interface external calls - and given its an external dependency, injecting it from the outside is not a bad thing.