TDD using MOQ

Ashwin. Shetty

3.17/5 (8 votes)

Feb 18, 2014

CPOL

2 min read

39142

Test Driven development using Mocking Framework

Introduction

In this article I would explaining how to use a mocking framework for test driven development. Sample in the current article are be developed using MOQ (mocking framework) . I am using Visual Studio 2013 IDE for development.

Background

Lot of developments now are getting focus on test driven development. Test driven development does increase development affords but it also saves us from code defects. Every time you develop a code write a unit test against it. This will save guard your code from any invalid code or bug which might get injected while developing new module or bugs fixes. Every time there’s a code change make sure you are executing test against it.

Writing unit test with 100% code coverage is also equally important. We will discuss code coverage some time later.

Using the code

Before we start coding, let’s add reference to MOQ using NuGet. This will setup required reference DLL in our project.

Say we have class which needs to deactivate a customer if he is already in active mode. We have implemented this logic in business layer. At the time of test we do not wish hit our database. Our database access layer is interface driven implementation & interface looks like this

public interface ICustomer
    {
        bool IsActive { get; set; }
        bool DeActivate();
    }

Business Layer code will look like this. Business layer will take Data access layer as input parameter in it constructor. By injecting data layer as parameter we are not tightly bidding our code with data layer. This will also help us in injecting mock object for testing.

 public class BLCustomer
    {
        protected ICustomer _Customer = null;
        public BLCustomer(ICustomer customer)
        {
            _Customer = customer;
        }

        public void DeActivateCustomer()
        {
            if (_Customer.IsActive)
            {
                _Customer.DeActivate();
            }
        }
    }

Before we start with our implementation, please make a note that using MOQ you can only mock Interface, Abstract Class & Public method which are been marked as virtual.

Add namespace MOQ to your namespace using list. Create Mock data access instance using Moq.Mock class

 Mock<ICustomer> mockCustomerDl = new Mock<ICustomer>();

Now we need to setup our instance to return true when we verify IsActive property. This is how we can do it.

 mockCustomerDl.SetupGet(prop => prop.IsActive).Returns(true);

Here we are using SetupGet method to mock ICustomer property IsActive. This will let Mock Instance know that it should always return true when we access get from IsActive property. We are using Lambda expression to access list of property inside ICustomer interface. Similarly to mock DeActivate method we will have to use Moq.Mock.Setup. Below is the code to setup DeActivate method.

 mockCustomerDl.Setup(meth => meth.DeActivate()).Returns(true);

Now only pending item is to inject mock object inside Customer business layer. To access mock we need to use Object property of mock instance

BLCustomer blCustomer = new BLCustomer(mockCustomerDl.Object);

Now our code it read for testing using Mock framework. Complete code will look like this

 Mock<ICustomer> mockCustomerDl = new Mock<ICustomer>();
 mockCustomerDl.SetupGet(prop => prop.IsActive).Returns(true);
 mockCustomerDl.Setup(meth => meth.DeActivate()).Returns(true);
 BLCustomer blCustomer = new BLCustomer(mockCustomerDl.Object);
 blCustomer.DeActivateCustomer();

Now when we execute our code it will not make a call to actual data access layer but this request will be routed to Mock object.

There are some more interesting Mock feature available under MOQ. I have listed some of them for your reference.

Mock.Verify
Mock.SetupSet
Moq.Times