Moq behaviour with virtual property and parameter constructor

Question

while mocking an object using parametrized constructor, if the property being initialized within the constructor is virtual, Moq does not set property value. But if it is non-virtual property, Moq sets the value.

Following is my class I wants to mock.

public class Activity
{
    private Activity() {}
    public Activity(string code, string description, string option)
    {
        if(string.IsNullOrEmpty(code)) throw  new ArgumentNullException("code");
        if (string.IsNullOrEmpty(option)) throw new ArgumentNullException("option");

        Code = code;
        Description = description;
        Option = option;
    }

    public virtual string Code { get; private set; }
    public virtual string Description { get; private set; }
    public virtual string Option { get; private set; }

}

This is how I try to mock it:

    [TestMethod]
    public void It_Creates_Mock_For_A_Class()
    {
        var mock = new Mock<Activity>("Code 1", null, "Option");
        Assert.IsNotNull(mock.Object);
        Assert.AreEqual("Code 1", mock.Object.Code);
    }

The test method fails saying: Assert.AreEqual failed. Expected:. Actual:<(null)>.

But if I remove the virtual keyword from all the property, it works and passes the test case.

I have to keep the properties virtual because of Entity Framework.

Any clue? How to get around this problem?

Actually your test tests MOQ framework instead of testing your implementation of constructor. What do you want to test? Do you ask about strange MOQ behaviour only? — Ilya Palkin
@IlyaPalkin Above was just an example to demonstrate the problem I was facing with Moq in case of virtual/non-virtual property. Due to this problem many of the behavioural test cases I was trying to write were failing, as internally the private methods of the Activity Class uses these properties and finding them null. — 101V

101V 101V · Accepted Answer · 2013-10-23T12:22:47

Found out that if "CallBase" property is set to true, it solved the problem.

By looking at the assembly in Object Browser, the summary says:

Summary: Whether the base member virtual implementation will be called for mocked classes if no setup is matched. Defaults to false.

The code that works:

    [TestMethod]
    public void It_Creates_Mock_For_A_Class()
    {
        var mock = new Mock<Activity>("Code 1", null, "Option");
        mock.CallBase = true;
        Assert.IsNotNull(mock.Object);
        Assert.AreEqual("Code 1", mock.Object.Code);
    }

Moq behaviour with virtual property and parameter constructor

1 Answers