使用回调验证呼叫顺序

当你不能/不想使用 Strict Mocks 时，你无法使用 MockSequence 来验证呼叫顺序。另一种方法是使用回调来验证是否按预期顺序调用了 Setup 期望。给出以下测试方法：

public void MethodToTest()
{
    _utility.Operation1("1111");
    _utility.Operation3("3333");
    _utility.Operation2("2222");
}

它可以测试如下：

// Create the mock (doesn't have to be in strict mode)
var utilityMock = new Mock<IUtility>();

// Create a variable to track the current call number
int callOrder = 1;

// Setup each call in the sequence to be tested.  Note that the callback validates that
// that callOrder has the expected value, then increments it in preparation for the next
// call.
utilityMock.Setup(x => x.Operation1(It.IsAny<string>()))
           .Callback(() => Assert.AreEqual(1, callOrder++, "Method called out of order") );
utilityMock.Setup(x => x.Operation2(It.IsAny<string>()))
           .Callback(() => Assert.AreEqual(2, callOrder++, "Method called out of order") );
utilityMock.Setup(x => x.Operation3(It.IsAny<string>()))
           .Callback(() => Assert.AreEqual(3, callOrder++, "Method called out of order") );

// Invoke the method to be tested
var sut = new SystemUnderTest(utilityMock.Object);
sut.MethodToTest();

// Validate any parameters that are important, note these Verifications can occur in any
// order.
utilityMock.Verify(x => x.Operation2("2222"));
utilityMock.Verify(x => x.Operation1("1111"));
utilityMock.Verify(x => x.Operation3("3333"));