Moq: Setup a mocked method to fail on the first call, succeed on the second

Question

What's the most succinct way to use Moq to mock a method that will throw an exception the first time it is called, then succeed the second time it is called?

Answer 1

I would make use of Callback and increment a counter to determine whether or not to throw an exception from Callback.

[Test] public void TestMe() {     var count = 0;     var mock = new Mock<IMyClass>();     mock.Setup(a => a.MyMethod()).Callback(() =>         {             count++;             if(count == 1)                 throw new ApplicationException();         });     Assert.Throws(typeof(ApplicationException), () => mock.Object.MyMethod());     Assert.DoesNotThrow(() => mock.Object.MyMethod()); }  public interface IMyClass {     void MyMethod(); } 

Answer 2

Starting with Moq 4.2 you can just use the built-in method SetupSequence() (as stated by @RichardBarnett comment).

Example:

var mock = new Mock<IMyClass>(); mock.SetupSequence(x => x.MyMethod("param1"))     .Throws<MyException>()     .Returns("test return");