248 words (approximately 2 mins)

overview

Argument matchers can be used for configuring and verifying methods and properties.

Some test examples below use this system:

public class Service
{
    private readonly IFoo _foo;

    public Service(IFoo foo) => _foo = foo ?? throw new ArgumentNullException(nameof(foo));

    public void Ping() => _foo.DoSomething("PING");
}

public interface IFoo 
{
    bool DoSomething(string command);
}

And are arranged like this:

var mock = new Mock<IFoo>();

var sut = new Service(mock.Object);

configuring method calls with matchers

It.Is<T> for any instance of T

When DoSomething() is called with any string argument, it should return true:

mock.Setup(mock => mock.DoSomething(It.IsAny<string>())).Returns(true);

It.IsInRange for any value in a range

When Add() is called with any integer in the range [0, 10], it should return true:

mock.Setup(mock => mock.Add(It.IsInRange<int>(0, 10, Range.Inclusive))).Returns(true);

It.Ref<T>.IsAny for any value of a ref parameter

When Submit() is called with any ref parameter of type Bar, it should return true:

mock.Setup(mock => mock.Submit(ref It.Ref<Bar>.IsAny)).Returns(true);

It.IsRegex for any string that matches a regular expression pattern

When DoSomethingStringy() is called with a string that matches regular expression pattern "[a-d]+", it should return "foo":

mock.Setup(x => x.GetUsername(It.IsRegex("[a-d]+", RegexOptions.IgnoreCase))).Returns("foo");

InSequence for verifying the calling sequence

This specifies that DoWithInteger() must be called, followed directly by DoWithDate(). Use MockBehavior.Strict to throw exceptions for non-configured calls:

var mockFirst = new Mock<IFirstService>(MockBehavior.Strict);
var mockSecond = new Mock<ISecondService>(MockBehavior.Strict);

var sequence = new MockSequence();

mockFirst.InSequence(sequence).Setup(p => p.DoWithInteger(1));
mockSecond.InSequence(sequence).Setup(p => p.DoWithDate(DateTime.Today));

a delegate

When Add() is called with a Func<int>, it should return true:

mock.Setup(mock => mock.Add(It.Is<int>(i => i % 2 == 0))).Returns(true);