How to test for exceptions thrown using xUnit, SubSpec and FakeItEasy

回眸只為那壹抹淺笑 提交于 2019-12-21 03:33:36

问题


I’m using xUnit, SubSpec and FakeItEasy for my unit tests. I’ve so far created some positive unit tests like the following:

"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));

But now I want to write some negative unit tests and check that certain methods don't get called, and an exception is thrown

e.g.

"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 
     );

I can see FakeItEasy has a MustNotHaveHappened extension method, and xUnit has an Assert.Throws method.

But how do I put it all together?

The exception I want to test for should occur when the Save method is called. So I’m guessing I should wrap an Assert.Throws method around the presenter.Save() method call, but I thought the presenter.Save method should be called in the .Do(() => ...

Can you please advise if my unit test should look like below or something else?

"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());

Many thanks


回答1:


I would do it like this:

"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()
     );

Or better still, switching SubSpec for xBehave.net and introducing 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());



回答2:


I've not heard of fakeItEasy or subSpec (You're tests look pretty funky, so I might check these out :)). However, I do use xUnit so this may be helpful:

I use Record.Exception with Assert.ThrowsDelegate

So something like:

    [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);
    }

Hope that helps.




回答3:


This is one way to do it in FakeItEasy.

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


来源:https://stackoverflow.com/questions/11013025/how-to-test-for-exceptions-thrown-using-xunit-subspec-and-fakeiteasy

易学教程内所有资源均来自网络或用户发布的内容,如有违反法律规定的内容欢迎反馈
该文章没有解决你所遇到的问题?点击提问,说说你的问题,让更多的人一起探讨吧!