c# - 如何使模拟第一次抛出异常并在第二次返回值

Question

我使用 Moq 作为我的模拟框架，我需要测试一个类，当特定类型的异常运行时，它会继续尝试，直到情况得到解决，一旦发生，执行完成。

所以我需要的是类似于:

myMock = Mock<IFoo>();

myMock.Setup(m => m.Excecute()).Throws<SpecificException>();
myMock.Setup(m => m.Execute());

var classUnderTest = MyClass(myMock);
classUnderTest.DoSomething();

Assert.AreEqual(expected, classUnderTest.Result);

感谢您提供的任何帮助。

Answer 1

这是一种方式，基于Moq QuickStart每次调用返回不同值的示例。

var mock = new Mock<IFoo>();
var calls = 0;
mock.Setup(foo => foo.GetCountThing())
    .Returns(() => calls)
    .Callback(() =>
     {
        calls++;
        if (calls == 1)
        {
            throw new InvalidOperationException("foo");
        }
     });

try
{
    Console.WriteLine(mock.Object.GetCountThing());
}
catch (InvalidOperationException)
{
    Console.WriteLine("Got exception");
}

Console.WriteLine(mock.Object.GetCountThing());

如果方法返回void，使用:

var myMock = new Mock<IFoo>();
bool firstTimeExecuteCalled = true;

myMock.Setup(m => m.Execute())
      .Callback(() =>
       {
            if (firstTimeExecuteCalled)
            {
                firstTimeExecuteCalled = false;
                throw new SpecificException();
            }
       });

try
{
    myMock.Object.Execute();
}
catch (SpecificException)
{
    // Would really want to call Assert.Throws instead of try..catch.
    Console.WriteLine("Got exception");
}

myMock.Object.Execute();
Console.WriteLine("OK!");