Mock objects - Setup method - Test Driven Development

Question

I am learning Test Driven Development and trying to use Moq library for mocking. What is the purpose of Setup method of Mock class?

Answer 1

The default behaviour of a Moq Mock object is to stub all methods and properties. This means that a call to that method/property with any parameters will not fail and will return a default value for the particular return type.

You call Setup method for any or all of the following reasons:

• You want to restrict the input values to the method.

public interface ICalculator {   int Sum(int val1, val2); }  var mock = new Mock<ICalculator>(); mock.Setup(m=>m.Sum(   It.IsAny<int>(), //Any value   3                //value of 3 )); 

The above setup will match a call to method Sum with any value for val1 and val2 value of 3.

• You want to return a specific value. Continuing with ICalculator example, the following setup will return a value of 10 regardless of the input parameters:

var mock = new Mock<ICalculator>(); mock.Setup(m=>m.Sum(   It.IsAny<int>(), //Any value   It.IsAny<int>()  //Any value )).Returns(10); 

• You want to use Mock<T>.VerifyAll() after you setups to verify that all previous setups have been called (once).

var mock = new Mock<ICalculator>(); mock.Setup(m=>m.Sum(   7, //value of 7   3                //value of 3 ));  mock.Setup(m=>m.Sum(   5, //value of 5   3                //value of 3 ));  mock.VerifyAll();     

The above code verifies that Sum is called twice. Once with (7,3) and once with (5,3).