title: ngrx + marble testing + delay
body: <p>Let's say I have an effect</p>
  
  <pre><code>@Effect()
  someEffect$ = this.actions$.pipe(ofType(X), switchMap(() =&gt; 
  of(Y).pipe(delay(3000)))
  </code></pre>
  
  <p>How should marble test look like?</p>
  
  <pre><code>const action = new X();
  const result = new Y();
  
  actions$.stream = hot('-x', { x: action });
  const expected = cold('-y', { y: result }); // ? adding frames or 3s doesn't work
  expect(effects.someEffect$).toBeObservable(expected);
  </code></pre>
  
  <p>In return I get</p>
  
  <pre><code>Expected $.lenght = 0 to equal 1. 
  </code></pre>