如何使用 xUnit、SubSpec 和 FakeItEasy 测试抛出的异常

Question

我使用 xUnit、SubSpec 和 FakeItEasy 进行单元测试。 到目前为止，我已经创建了一些积极的单元测试，如下所示：

"Given a Options presenter"
    .Context(() =>
        presenter = new OptionsPresenter(view,
                                         A<IOptionsModel>.Ignored,
                                         service));

"with the Initialize method called to retrieve the option values"
    .Do(() => 
        presenter.Initialize());

"expect the view not to be null"
    .Observation(() =>
        Assert.NotNull(view));

"expect the view AutoSave property to be true"
    .Observation(() => Assert.True(view.AutoSave));

但是现在我想写一些负面的单元测试并检查某些方法没有被调用，并抛出异常

例如

"Given a Options presenter"
    .Context(() =>
        presenter = new OptionsPresenter(view,
                                         A<IOptionsModel>.Ignored,
                                         service));

"with the Save method called to save the option values"
    .Do(() => 
        presenter.Save());

"expect an ValidationException to be thrown"
    .Observation(() =>
        // TODO 
     );

"expect an service.SaveOptions method not to be called"
    .Observation(() =>
        // TODO 
     );

我可以看到 FakeItEasy 有一个 MustNotHaveHappened 扩展方法，而 xUnit 有一个 Assert.Throws 方法。

但是我该如何把它们放在一起呢？

我要测试的异常应该在调用 Save 方法时发生。所以我猜我应该在 presenter.Save() 方法调用周围包装一个 Assert.Throws 方法，但我认为应该在 .Do(() => ...

中调用 presenter.Save 方法

您能否告知我的单元测试是否应该如下所示或其他？

"Given a Options presenter"
    .Context(() =>    
        presenter = new OptionsPresenter(view,
                                         model,
                                         service));

"expect the Presenter.Save call to throw an Exception"
    .Observation(() =>
        Assert.Throws<FluentValidation.ValidationException>(() => presenter.Save()));

"expect the Service.SaveOptions method not to be called"
    .Observation(() =>
        A.CallTo(() => service.SaveOptions(A<IOptionsModel>.Ignored)).MustNotHaveHappened());

非常感谢

Answer 1

我没有听说过 FakeItEasy 或 SubSpec（你的测试看起来很时髦，所以我可能会检查一下 :)）。但是，我确实使用 xUnit，所以这可能会有所帮助：

我将 Record.Exception 与 Assert.ThrowsDelegate 一起使用

比如：

    [Fact]
    public void Test()
    {
        // Arange

        // Act
        Exception ex = Record.Exception(new Assert.ThrowsDelegate(() => { service.DoStuff(); }));

        // Assert
        Assert.IsType(typeof(<whatever exception type you are looking for>), ex);
        Assert.Equal("<whatever message text you are looking for>", ex.Message);
    }

希望对您有所帮助。

Answer 2

我会这样做：

"Given a Options presenter"
    .Context(() =>
        presenter = new OptionsPresenter(view,
                                         (IOptionsModel)null,
                                         service));

"with the Save method called to save the option values"
    .Do(() => 
        exception = Record.Exception(() => presenter.Save()));

"expect an ValidationException to be thrown"
    .Observation(() =>
        Assert.IsType<ValidationException>(exception)
     );

"expect an service.SaveOptions method not to be called"
    .Observation(() =>
        A.CallTo(() => service.SaveOptions(A<IOptionsModel>.Ignored)).MustNotHaveHappened()
     );

或者更好的是，将 SubSpec 切换为 xBehave.net 并引入 FluentAssertions:-

"Given an options presenter"
    .x(() => presenter = new OptionsPresenter(view, (IOptionsModel)null, service));

"When saving the options presenter"
    .x(() => exception = Record.Exception(() => presenter.Save()));

"Then a validation exception is thrown"
    .x(() => exception.Should().BeOfType<ValiationException>());

"And the options model must not be saved"
    .x(() => A.CallTo(() =>
        service.SaveOptions(A<IOptionsModel>.Ignored)).MustNotHaveHappened());

Answer 3

这是 FakeItEasy 中的一种方法。

Action act = () => someObject.SomeMethod(someArgument);
act.ShouldThrow<Exception>();