public async Task TestCommandSubscription()
        {
            var testScheduler = new TestScheduler();

            using (var busyStatusMonitor = new BusyStatusMonitor(testScheduler))
            {
                Assert.False(busyStatusMonitor.IsBusy);
                var command = ReactiveCommand.Create(() => { }, null, Scheduler.Immediate);
                busyStatusMonitor.AddCommand(command, "command");

                var list = new List <bool>();
                using (busyStatusMonitor.Subscribe(x => list.Add(x)))
                {
                    await command.Execute();

                    testScheduler.AdvanceBy(2);
                    Assert.Equal(true, list.Last());
                    testScheduler.AdvanceBy(1);
                    Assert.Equal(false, list.Last());
                }
            }
        }