CODEWITHSUNDEEP
angularunit-testing
SWeko
SWeko

Reputation: 30892

How to test promises with HttpTestingController?

In an angular 2 application, I have a data service that converts the http observables to promises, in order to use the async/await sweetness, something like this:

async getCustomer(id: number): Promise<Customer> {
   return await this._http.get<Customer>(`${this.serverUrl}/customer/${id}`).toPromise();
}

This is operational and looks and works great.

My previous unit tests used the MockBackend with something like

mockBackend.connections.subscribe(c => {
   expect(c.request.url).toBe(`${serverUrl}/customer/${id}`);
   let response = new ResponseOptions({ body: mockResponseBody });
   expect(c.request.method).toBe(RequestMethod.Get);
   c.mockRespond(new Response(response));
});

let actual = await service.getCustomer(id);

However, now when I try something like this with 

httpMock = TestBed.get(HttpTestingController);
// ... 1
let actual = await service.getCustomer(id);
// ... 2

I'm getting in a chicken-and-egg situation. The getCustomer method will not return until a mocked request is provided, and I cannot use httpMock.expectOne or httpMock.match until the http call is triggered.
So if I put a httpMock call in [1], I'm getting an expectation fail, and if I put it in [2], I'm getting a timeout error :(

Is there a way around this?

Upvotes: 1

Views: 2214

Answers (1)

Tamas Hegedus
Tamas Hegedus

Reputation: 29916

I don't know how TestBed exactly works. I don't see why does it prevent you from installing a mock before the getCustomer call is made. You should use a framework that lets you do so.

But it is possible to do with the current setup: just postpone awaiting on the promise!

httpMock = TestBed.get(HttpTestingController);
let customerPromise = service.getCustomer(id);
let request = httpMock.expectOne('http://myurl.com'); 
let actual = await customerPromise;

Upvotes: 5

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