Using Moq ExpectSet

I am trying out Moq, having used RhinoMocks a fair bit in the past.

I was having trouble using the ExpectSet method which verifies that a property has been set, and a Google search found nothing that directly answered my question. I wanted to know how to verify that the value set is what was expected.

It turns out that you need to define a callback in which you have the assertion to verify that the property has been set to the correct value.

[TestMethod]
public void TestAppleShiner() {

    // Mock the interface being passed to the class to be tested
    var fruit = new Mock<IFruit>();

    // Define the expectation that the Colour property will be
    // set to Green
    fruit.ExpectSet(f => f.Colour).Callback(
        setColor => Assert.AreEqual("Green", setColor)).Verifiable();

    // Run the test
    ApplePolisher applePolisher = new ApplePolisher();
    applePolisher.Polish(fruit.Object);

    // Verify that the test passed (note .Verifiable on the ExpectSet)
    fruit.VerifyAll();
}

public interface IFruit {
    string Colour { get; set; }
}

public class ApplePolisher {
    public void Polish(IFruit fruit) {
        fruit.Colour = "Green";
    }
}

After ExpectSet, call the Callback method, giving the name of the variable to hold the passed-in value, and then the assertion with regards to its value.