What other interesting things can we test? We can test whether the first exercise has started. We add this test to workout.spec.ts after the one we just added:

it('should start the first exercise', () => { 
    spyOn(runner, 'startExercise').and.callThrough(); 
    runner.ngOnInit(); 
    runner.ngDoCheck(); 
    expect(runner.currentExerciseIndex).toEqual(0); 
    expect(runner.startExercise).toHaveBeenCalledWith(
    runner.workoutPlan.exercises[runner.currentExerciseIndex]); 
    expect(runner.currentExercise).toEqual(
    runner.workoutPlan.exercises[0]); 
}); 

The second expect function in this test is interesting. It uses a Jasmine feature: spies. Spies can be used to verify method invocations and dependencies.