在angular4单元测试中处理异步调用的正确方法

Question

I have been searching for correct method to test GraphQL asynchronous calls in Angular 4 unit test using Jasmine. What is the correct flow of testing asynchronous calls without using setTimeout function ? This is my current code but not waiting for response

it('shoud swap', (done) => {
const SequenceMaster = '0';
const sequenceMasterAlts = '2138';
const sKey = '[DARCARS]SS_02_VW+201701_VW';
component.swapTablesData(sKey);
  expect(component.testVariable).toBe(true);
  done();
 });

Answer 1

Docs are explaining pretty nice though and you can do this using fakeAsync :

describe('test service using fakeAsync', fakeAsync(() => {
    let service: SomeService;

    beforeEach(() => {
        TestBed.configureTestingModule({ providers: [SomeService] });

        service = TestBed.get(SomeService, null);
    });

    it('should use SomeService', () => {
        let returnValue: any;
        service.doSomething().then((val: any) => returnValue = val);
        tick();
        expect(returnValue).toBe('return value using fakeAsync');
    });
});