Unit Testing complex Observable flows

Question

I have the following function, which (I think) returns a compound observable: ``` test(cell) { const observ1 = this.store.select('range').flatMap((val: IRange) => {return this.getCellOEE(val.value)}); const observ2 = this.getCellOEE(cell); return Observable.merge(observ1, observ2); } ``` I am using this in an angular 4 service, and trying to unit test with jasmine and karma. So I am mocking store like this: ``` class mockStore { select(): Observable<IRange> { return Observable.of({value: 'daily', start: moment(), end: moment()}, {value: 'monthly', start: moment(), end: moment()}) } } ``` and then I have the following test: ``` it('should update result on store change', fakeAsync(inject( [MockBackend, OeeService], (backend: MockBackend, s: OeeService) => { const urls = []; backend.connections.subscribe((connection: MockConnection) => { const req: any = connection.request; urls.push(req.url); if (req.method === RequestMethod.Get && req.url === 'api/getLine/data' req.headers.get('range')…

Accepted Answer

You are right, there is a timing issue with the test. By the time the first `Expect()` expression occurs, both mock `Responses` have returned. To fix your test, you can change one of the responses to use `setTimeout()` and set the `tick()` between expect clauses to some time after that delay.

eg:

```
if (req.method === RequestMethod.Get && req.url === 'api/getLine/data' && req.headers.get('range') === 'monthly') {
    setTimeout(() => { 
        connection.mockRespond(new Response(new ResponseOptions({ body: { data: 15 } })));      }, 100);
}
```

and:

```
expect(value).toEqual(12);
tick(100);
expect(value).toEqual(15);
```

However, similarly to what julia said above, a better test would be to push the values into an array and check that the values at the respective indexes are correct. In this case I would recommend replacing `flatMap()` in your test function with `concatMap()`, which preserves order. You can then write multiple tests with each response delayed and still check that the values at the respective indexes are correct:

```
tick(100);
expect(values[0]).toEqual(12);
expect(values[1]).toEqual(15);
```

Unit Testing complex Observable flows

Solution

Problem