How to Unit Test a Function that Overwrites an Aurelia Component

gistfile1.md

To cover this particular function one needs to call app.configHttpClient() either directly, or by calling app.activate().

The httpClient is aurelia's fetch wrapper (docs: http://aurelia.io/hub.html#/doc/article/aurelia/fetch-client/latest/http-services/2) which is initialized in the App's constructor.

By default it's @injected by aurelia

…
import {inject} from 'aurelia-framework';
import {HttpClient} from 'aurelia-fetch-client';

@inject(Router, FetchConfig, AuthService, AppRouterConfig, HttpClient)
export class App {
  constructor(router, fetchConfig, auth, appRouterConfig, httpClient){
    this.router = router;
    …
    this.httpClient = httpClient;
  }

but in the test (app.spec.js) it's stubbed with a class HttpStub in beforeEach.

class HttpStub { configure(){…} }
…
  beforeEach(() => {
    app1 = new App(null, null, new AuthStub(), new RouterStub(), new HttpStub());

The configure function in this stub can then validate the function passed to it (httpConfig => { httpConfig…), whcih is exactly what I've done:

it('tests configHttpClient', () => {
  app1.configHttpClient();
  app1.httpClient.__configureCallback(new (class {
    withDefaults() {return this}
    withInterceptor() {return this}
  })())
});

Here the httpClient.__configureCallback was defined to store the callback passed to httpClient.configure when called in the stub:

class HttpStub {
  configure(fn) {
    this.__configureCallback = fn
    return this.__configureReturns;
  }

Gist provided by Freeth Lua