Why does my Moq claim no invocations are being thrown, yet it displays the thrown invocation in the exception?

I have the following unit test:

[TestMethod]
public void Execute_Sends_Email_To_User()
{
    // Setup
    InitializeTestEntities();
    _mock.Setup(x => x.Send(It.Is<string>(y => y == _us开发者_运维知识库er.Email), 
        It.IsAny<string>(), It.IsAny<string>()));

    // Act
    new ResetUserPasswordCommand(_unitOfWork, 
        _mock.Object).WithUserId(_user.Id).Execute();

    // Verify
    _mock.Verify(x => x.Send("", "", ""), Times.Once());
}

When this runs, I get the following exception message

Test method 
MyApp.Tests.Commands.Users.ResetUserPasswordCommandTests.Execute_Sends_Email_To_User 
threw exception: 

Moq.MockException: 
Expected invocation on the mock once, but was 0 times: x => x.Send("", "", "")

Configured setups:
x => x.Send(It.Is<String>(y => y == ._user.Email), It.IsAny<String>(), 
    It.IsAny<String>()), Times.Once

Performed invocations:
IEmailUtils.Send("test@email.com", "Password Recovery", 
    "Your new password is: 7Xb79Vb9Dt")

I'm confused about this, because it says that the mock was invoked 0 times, yet it shows that the successful invocation. What am I doing wrong?

you need

_mock.Verify(x => x.Send(
     It.IsAny<String>(), It.IsAny<String>(), It.IsAny<String>(), Times.Once());

cause it does not match the arguments passed in. Therefore it thinks it didn't call that method with those arguments.

You can Verify that the specific strings are passed into the mock method, but that will depend on what you are trying to test

In your particular case there is no point to the Setup method as the Verify will still work. Only when you need to return a value from a mocked method do you really need to use Setup.

If parameter count doesn't match or their type doesn't match nunit will give compile time error but in my case I used It.IsAny<int> instead of It.IsAny<long> and it did not give any compile error but the test failed. Later, I realized data type while mocking has to be exact.