in tests mux.Vars() returns nil instead of expected map

Question

I have a Gorilla Mux router setup inside a function that returns *mux.Router, goes like this

func MakeApp(services service.Service, pe PolicyEnforce) *mux.Router {
    app := mux.NewRouter()

    app.NotFoundHandler = &NotFound{}

    app.Use(token.TokenMiddleware)

    # ...
    
    app.Methods(http.MethodPost).Path("/api/v1/subscription/{emisor}/mh").HandlerFunc(MakeUpdateMH(services, pe))
    app.Methods(http.MethodGet).Path("/api/v1/subscription/{emisor}/mh").HandlerFunc(MakeGetMH(services, pe))
    app.Methods(http.MethodPost).Path("/api/v1/subscription").HandlerFunc(MakeCreateSubscription(services, pe))
    app.Methods(http.MethodGet).Path("/api/v1/subscription/{emisor}").HandlerFunc(MakeGetSubscription(services, pe))
    
    # ...

    return app
}

So, on my tests I prepare the handle with an URL and run it:

func (suite *AppTestSuite) TestUpdateMH() {
    args := &service.UpdateMHInput{
        Usuario:     new(string),
        Clave:       new(string),
        Pin:         new(string),
        Certificado: new(string),
        Actividades: []string{},
    }
    reader, err := makeBody(args)
    suite.NoError(err)

    handle := token.TokenMiddleware(transport.MakeUpdateMH(suite._s, suite.pe))

    req := httptest.NewRequest(http.MethodPut, "/api/v1/subscription/-/mh", reader)
    w := httptest.NewRecorder()

    t := genToken([]v43.Rol{
        {
            Nombre: "mh",
            Permisos: []v43.Permiso{{
                Sujeto: permission.MHCredentials,
                Accion: permission.Update,
            }},
        },
    })
    req.Header.Add("Authorization", t)

    // configura repository
    suite.r.On("UpdateIssuerMH", emisor, args.Usuario, args.Clave, args.Pin, args.Certificado, args.Actividades).Return(v43.Grupo{}, nil)
    handle.ServeHTTP(w, req)

    resp := w.Result()

    suite.Equal(http.StatusOK, resp.StatusCode, resp.Status)
}

Inside the handle things look like this:

func MakeUpdateMH(s service.Service, p PolicyEnforce) http.HandlerFunc {
    return func(w http.ResponseWriter, r *http.Request) {
        emisor := mux.Vars(r)["emisor"]

        // revisa permisos
        permitido := p.TienePermiso(r.Context(), permission.MHCredentials, permission.Update) && p.PuedeActuarSobreEmisor(r.Context(), emisor)
        if !permitido {
            reportError(w, fault.ErrPermissionDenied, http.StatusForbidden, fault.MessageForbidden, fault.MessageForbidden)
            return
        }
        // cambia el emisor afectado por aquel obtenido de la URL
        if emisor != "-" || emisor == "" {
            emisor = token.GetSub(r.Context())
        }

        var input service.UpdateMHInput
        dec := json.NewDecoder(r.Body)
        err := dec.Decode(&input)
        if err != nil {
            http.Error(w, fault.NewBackendError("no se pudo decodificar solicitud: %v", err).Error(), http.StatusBadRequest)
            return
        }

        output, err := s.UpdateMHCredentials(emisor, input.Usuario, input.Clave, input.Pin, input.Certificado, input.Actividades)
        if err != nil {
            http.Error(w, fault.NewBackendError("Error al actualizar credenciales de MH: %v", err).Error(), http.StatusInternalServerError)
            return
        }

        enc := json.NewEncoder(w)
        enc.Encode(output)
    }
}

and I've noticed that mux.Vars(r) is returning nil instead of the map of values, which should contain {"emisor": "-"} and I cannot understand why this is not the case.

I'm already handling the case for when "emisor" is empty, but for other routers where "-" or empty string cannot be used this quirk is causing me troubles, what am I doing wrong, and how can I still run my tests successfully without having to manually inject my Vars? and also: will this issue translate into production?

Answer 1

My setup is wrong, I'm not using *mux.Router in my tests but calling the handlers directly. If I wanted to use the *mux.Router returned by my function MakeApp then I'll need to put that inside a test HTTP server using net/http/httptest.