How to set URL parameters for unit tests?

[bhirbec]

Hi,

I need to set up URL parameters for my unit tests. I'm using context.Set() to do so and my test looks something like this:

context.Set(r, 0, map[string]string{"param1": "123"})
req , _ := http.NewRequest()
w = := httptest.NewRecorder()
myhandler(w, req)

The HTTP handler uses mux.Vars() to retrieve the parameters but it doesn't get any. The problem is explained in great details in this post:

Trouble is, even when you use 0 as value to set context values, it is not same value that mux.Vars() reads. mux.Vars() is using varsKey (as you already saw) which is of type contextKey and not int.

Sure, contextKey is defined as:

type contextKey int

which means that it has int as underlying object, but type plays part when comparing values in go, so int(0) != contextKey(0).

I'm aware I could solve my problem by either starting a web server or by calling the mux directly (as mentioned in SO). However, I don't want to do so. I'd like to call the handler directly in my test.

I see two options to solve this:

• add a mux.SetVar() method to explicitly set URL parameters for a given request (there's already a private setVar() method)
• use int instead of contextKey type when defining varsKey. This way context.Set(r, 0, map[string]string{"param1": "123"}) would be a valid way to set up URL parameters.

Hope this help. Thanks for making Gorilla :)

Ben

[elithrar]

Note: also discussed in #112

The short answer: using https://golang.org/pkg/net/http/httptest/#Server + setting server.URL = /your/test/url is the right way to test this. You can still test multiple handlers, use table driven tests for testing different route variables, etc - without tying your tests to mux's implementation.

The long answer: changing the type of contextKey to int would cause collisions with other packages also using the request context. The gorilla/context docs cover this. Making the key type public would also add to the API and prevent us from ever changing things.

[bhirbec]

@elithrar thanks for the reply. I'm not sure to understand your solution. How does the context get populated if the mux isn't involved? Can you please provide more informations or point to an example?

[elithrar]

@bhirbec You populate the context by passing the correct URL - e.g.

    r := mux.NewRouter()
    r.HandleFunc("/hello/{name}", http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        fmt.Fprintln(w, "Hello, client")
    }))

    ts := httptest.NewServer(r)
    defer ts.Close()

    // Table driven test
    names := []string{"kate", "matt", "emma"}
    for _, name := range names {
        url := ts.URL + "/hello/" + name
        resp, err := http.Get(url)
        if err != nil {
            t.Fatal(err)
        }

        if status := resp.Code; status != http.StatusOK {
            t.Fatalf("wrong status code: got %d want %d", status, http.StatusOK)
        }
    }

This way—regardless of whether you use gorilla/mux or not—you're still testing that your application handles the route variables you're passing.

[elithrar]

Closing this out for now. Re-open if any questions!

[bkeroackdsc]

@elithrar For the love of all that is holy, please just expose a SetVars function. The implementation behind it will be opaque so it preserves separation of concerns, and it will allow us to test our handlers in isolation without having to spin up an entire HTTP server just to test a single function!

[astromahi]

It would be great help, if you guys export the setVars. It forcing me to do functional testing.

func setVars(r *http.Request, val interface{}) *http.Request {
	return contextSet(r, varsKey, val)
}

[vincent6767]

Any update on this?

[elithrar]

@vincent6767 - https://godoc.org/github.com/gorilla/mux#SetURLVars

[vincent6767]

Yep. I have just seen them several hours ago. Thank you!

[bkeroackdsc]

Thanks @elithrar !

[palsivertsen]

Handy function for testing!
testing-handlers section in Readme could use this update

[elithrar]

@palsivertsen Would you like to PR that? :)

[palsivertsen]

@elithrar Sure. See pull #342