Question

我在测试ReactiveCommands及其执行能力方面遇到了麻烦。

鉴于以下视图模型：

    public class HowToTestViewModel : ReactiveObject
    {
        public ReactiveCommand<Unit> CommandThatDoesStuff { get; set; }
        public IObservable<bool> CanExecute { get; set; }

        public ObservableCollection<string> TheCollectionMustHaveItems { get; set; }

        public HowToTestViewModel()
        {
            TheCollectionMustHaveItems = new ObservableCollection<string>();

            this.CanExecute = this.WhenAnyValue(vm => vm.TheCollectionMustHaveItems)
                .Do(debug => Console.WriteLine("Can Execute Value: " + debug.Count()))
                .Where(col => col.Any())
                .Do(debug => Console.WriteLine("Can Execute (not empty?) Value: " + debug.Count()))
                .Select(x => true);

            CommandThatDoesStuff = ReactiveCommand.CreateAsyncTask(this.CanExecute, async param => {
                //web service or something...
                await Task.Delay(1000);
            });

            CommandThatDoesStuff.Subscribe(next => Console.WriteLine("The command fired and no exceptions were thrown."));

            CommandThatDoesStuff.ThrownExceptions.Subscribe(error => Console.WriteLine("boom. handle your business here."));

        }
    }

我想测试以确保命令无法执行，除非TheCollectionMustHaveItems不为空且有项目。

    [Test]
    public void CanExecute_spec()
    {
        (new TestScheduler()).With(sched =>
        {
            var sut = new HowToTestViewModel();

            sut.CommandThatDoesStuff.Execute(null);

            sut.CommandThatDoesStuff.CanExecute(null).Should().BeFalse();

            sut.TheCollectionMustHaveItems.Should().BeEmpty();

            sut.TheCollectionMustHaveItems.Add("item added"); //CanExecute should update

            sched.AdvanceBy(1000);

            sut.CommandThatDoesStuff.CanExecute(null).Should().BeTrue();

        });
    }

我正在使用TestScheduler，但我不知道为什么。我的问题是：

如何让测试通过？
我应该在命令上测试CanExecute吗？
我应该使用ToPropery和ObservableAsPropertyHelper而不是CanExecute的公共IObservable吗？

更新1

根据以下建议，我将ObservableCollection更改为ReactiveList，我（我想）我使用TheCollectionMustHaveItems.CountChanged来验证CommandThatDoesStuff是否可以执行。使用以下更新的VM和测试我得到相同的错误。

    public class HowToTestViewModel : ReactiveObject
    {
         ....

        public IReactiveList<string> TheCollectionMustHaveItems { get; set; }

        public HowToTestViewModel()
        {
            TheCollectionMustHaveItems = new ReactiveList<string>();

            this.CanExecute = this
                .TheCollectionMustHaveItems.CountChanged
                .Do(next => Console.WriteLine("logging the next result:" + next))
                .ObserveOn(RxApp.MainThreadScheduler)
                .Where(collection => TheCollectionMustHaveItems.Any())
                .Select(x => true);

        ...

        }
    }

更新2

将测试更新为await CommandThatDoesStuff会导致测试运行器永远不会返回。

    [Test]
        public async void CanExecute_spec()
        {
            await (new TestScheduler()).With(async sched =>
             {
             var sut = new HowToTestViewModel();

             await sut.CommandThatDoesStuff.ExecuteAsyncTask(null);

             sut.CommandThatDoesStuff.CanExecute(null).Should().BeFalse();

             sut.TheCollectionMustHaveItems.Should().BeEmpty();

             sut.TheCollectionMustHaveItems.Add("item added"); //CanExecute should update

             sut.CanExecute.Subscribe(next => next.Should().BeTrue());

             sched.AdvanceBy(1000);

             sut.CommandThatDoesStuff.CanExecuteObservable.Subscribe(next => next.Should().BeTrue());
         });
    }

Answer 1

WhenAnyValue不适用于ObservableCollection

最好的办法是使用ReactiveUI附带的ReactiveList并观察CountChanged属性。

Answer 2

首先，因为您使用.Where后跟.Select，所以CanExecute只会返回true个值。将其更改为：

this.CanExecute = this
    .TheCollectionMustHaveItems.CountChanged
    .Log(this, "next result")   // RxUI has a nice Log extension method that can replace your previous usage of Do
    .ObserveOn(RxApp.MainThreadScheduler)
    .Select(count => count > 0);

其次，async测试返回类型应为Task，而不是void。

测试ReactiveCommand和ReactiveObject ViewModels

更新1

更新2

2 个答案: