StoryQ场景，预计会出现异常

.Then

Action

Func

.Then

[Test]
public void AnIllegalOperationThrowsAnException()
{
    new Story("My Story)
        .InOrderTo("Do achieve something")
        .AsA("User")
        .IWant("To carry out an operation")
        .WithScenario("an exception occurs")
        .Given(InitialConditions)
        .When(TheIllegalActionIsTaken)
        .Then(AnIllegalOperationExceptionIsThrown);
}

private void InitialConditions()
{
}

private Func<string> _operation;

private void TheIllegalActionIsTaken()
{
    _operation = () => return MyTestClass.DoesSomethingWrong();
}

private void AnIllegalOperationExceptionIsThrown()
{
    try
    {
        _operation.Invoke();
        Assert.Fail("An exception should have been thrown");
    }
    catch (Exception ex)
    {
        Assert.That(ex, Is.InstanceOf<IllegalOperationException>(), "The wrong exception was thrown");
        Assert.That(ex.Message, Is.EqualTo("Ooops!");
    }
}

_action.ShouldThrow<IllegalOperationException>().WithMessage("Ooops!");