CallBase = true In Moq

Question

Hi team I am new to moq and not able to understand concept of

CallBase = true;
var mock = new Mock<IFoo> { CallBase = true };

According to git hub :Invoke base class implementation if no expectation overrides the member

But I have below test case in which i am able to mock base class member without using CallBase = true

// Creating Base class.
public abstract class Car
{  
   public virtual bool IsValidSpeed()
    {
        ///complex logic
        ///returnig false just to compile code
        return false;
    }
}

// Creating child class
public class Ferrari : Car
{
    public int Speed { get; set; }
     public void PrintSpeed(int speed)
    {
        if (IsValidSpeed())
        {
            Speed = speed;
        }
    }
}

Below writing test case. I am not setting property CallBase = true for my mock object

 public void MoqPracticeTest2()
 {
    //  var mock = new Mock<Ferrari>() { CallBase = true }; 
    var mock = new Mock<Ferrari>(MockBehavior.Strict);
    //Mocking Base class function
    mock.Setup(x=>x.IsValidSpeed()).Returns(true); 
    //calling function which will call base function
    mock.Object.PrintSpeed(100);
    //calling Verify on mock object
    mock.Verify(x => x.IsValidSpeed(), Times.Once);
    Assert.AreEqual(mock.Object.Speed,100); //Doing Assert
 }

still above test case is passing without setting callback property. can some one please explain use of CallBase = true here.

Answer 1

You don't need to set the CallBase to true, since you just want to verify that provided that IsValidSpeed() returns true, the speed of the Ferrari object would be the one provided to the PrintSpeed method.

So by declaring the following:

mock.Setup(x=>x.IsValidSpeed()).Returns(true);

you can simulate this specific scenario, without getting into the details on how IsValidSpeed is implemented.

On the other hand, just try this. Remove the above line and set the CallBase to true. This time you should note that the assertion would fail. This is due to the fact that the actual method would be called and the value of false would be returned, as you have already mentioned in your post. Hence in this case the value of provided speed would not be assigned to Speed.