如何使用 Moq 对不同参数设置两次方法

我想用最小起订量设置一个方法两次，但似乎最后一个方法覆盖了前面的方法。这是我的初始设置：

string username = "foo";
string password = "bar";

var principal = new GenericPrincipal(
    new GenericIdentity(username),
    new[] { "Admin" });

var membershipServiceMock = new Mock<IMembershipService>();
membershipServiceMock.Setup(ms =>
    ms.ValidateUser(username, password)
).Returns(new ValidUserContext { 
    Principal = principal
});

效果很好，但我希望它返回new ValidUserContext()如果用户名或密码与username and password变量如上。为此，我添加了另一个设置，但这一次它会覆盖上面的设置并始终应用它：

membershipServiceMock.Setup(ms =>
    ms.ValidateUser(It.IsAny<string>(), It.IsAny<string>())
).Returns(
    new ValidUserContext()
);

使用 Moq 处理此类情况的最优雅的方法是什么？

Edit

我用下面的方法解决了这个问题，但我想有更好的方法来处理这个问题：

var membershipServiceMock = new Mock<IMembershipService>();
membershipServiceMock.Setup(ms =>
    ms.ValidateUser(It.IsAny<string>(), It.IsAny<string>())
).Returns<string, string>((u, p) => 
    (u == username && p == password) ?
    new ValidUserContext { 
        Principal = principal
    }
    : new ValidUserContext()
);

Moq 支持开箱即用的参数约束：

mock.Setup(ms => ms.ValidateUser(
        It.Is<string>(u => u == username), It.Is<string>(p => p == password))
    .Returns(new ValidUserContext { Principal = principal });
mock.Setup(ms => ms.ValidateUser(
        It.Is<string>(u => u != username), It.Is<string>(p => p != password))
    .Returns(new ValidUserContext());

包罗万象 It.IsAny也可以，但顺序很重要：

// general constraint first so that it doesn't overwrite more specific ones
mock.Setup(ms => ms.ValidateUser(
        It.IsAny<string>(), It.IsAny<string>())
    .Returns(new ValidUserContext());
mock.Setup(ms => ms.ValidateUser(
        It.Is<string>(u => u == username), It.Is<string>(p => p == password))
    .Returns(new ValidUserContext { Principal = principal });