public void IsEnabledTest()
    {
        var testScheduler = new TestScheduler();
        var recorder      = testScheduler.CreateObserver <long>();

        var timer = new ReactiveTimer(TimeSpan.FromSeconds(1), testScheduler);
        var isEnabledChangedCounter = 0;

        timer.ObserveProperty(x => x.IsEnabled, false).Subscribe(_ => isEnabledChangedCounter++);
        timer.IsEnabled.IsFalse();
        timer.Start();
        timer.IsEnabled.IsTrue();
        timer.Stop();
        timer.IsEnabled.IsFalse();
        isEnabledChangedCounter.Is(2);
    }