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Fundamentals of Unit Testing: Understand AAA in Unit Testing

This is the fundamentals of the unit testing article series. In our previous article, we saw how to do unit testing in the Visual Studio environment. You can read them here.

In this short article, we will understand the “AAA” concept of unit testing. This is a very important and fundamental idea of unit testing. In the overall view of any unit test application, we will see that a unit test is a three-step process. The first one is setup test or arrange test, Act test or execute unit test and Assert means verify test result with expected results. The concept of three "A"s are given below.

  • Arrange: This is the first step of a unit test application. Here we will arrange the test, in other words, we will do the necessary setup of the test. For example, to perform the test we need to create an object of the targeted class, if necessary, then we need to create mock objects and other variable initialization, something like this.
  • Act: This is the middle step of a unit-step application. In this step, we will execute the test. In other words, we will do the actual unit testing and the result will be obtained from the test application. Basically, we will call the targeted function in this step using the object that we created in the previous step.
  • Assert: This is the last step of a unit test application. In this step, we will check and verify the returned result with the expected results.

Ok, fine we have understood the concept, so let's implement the three steps practically. So, create a class library application with the following code.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace TestProjectLibrary
{
    public class testClass
    {
        public Boolean testFunction()
        {
            return true;
        }
    }
}

This is the code that we will test. The code is very simple, the class contains only one function and it will always return true since we are not interested in writing the business logic at all.

Now, add one unit test application to the solution and the following is the code to do the unit testing of the code above. If you are very new to unit testing then I will suggest you go through our first article to understand unit test setup by a Visual Studio unit test application. Have a look at the following code.

using System;
using Microsoft.VisualStudio.TestTools.UnitTesting;
using TestProjectLibrary;
//using Moq;

namespace UnitTest
{
    [TestClass]
    public class UnitTest
    {
        [TestMethod]
        public void TestMethod()
        {
            //Arrange test
            testClass objtest = new testClass();
            Boolean result;

            //Act test
            result = objtest.testFunction();

            //Assert test
            Assert.AreEqual(true, result);
        }
    }
}

Here we clearly see three parts of the unit test, at first we are creating an object of the test class and then we declare one Boolean variable that will store the returned result, and in the next level, we check whether or not the return value is equal to the expected value.

Let's run the test and check the result.

Result

Conclusion

Oh, we see that it has been successfully executed and the test passed. I hope you have understood the concept of AAA in unit test applications.


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