Answer:
 

Unit testing is validation and verification technology where the developer tests the individual units of source code. These individual units can be functions, methods or class.

Below is the simple Math class which has a Add function with two input parameter. The Add function basically adds the number and gives the addition of these two numbers.

As a developer we would like to test is this Add function actually works properly or not.

namespace TestVSTS
{
public class Math    {
public int Add(int i, int j)       {
         int sum;
         sum = i + j;
         return sum;
      } }
}

In order to do unit testing by using VSTS the first thing you need to create a simple unit test. In visual studio team system (VSTS)they provide the test menu in which you can select the unit testing as you can see in the below diagrams.

After selecting unit test open the .cs file and write the logic in [TestMethod] attribute which you want to test.

[TestMethod]
public void Check()
     {
      Math obj = new Math();
      int r = obj.Calculate(10,20);
      Assert.AreEqual(30,r);
     }

Once you have completed the above steps, now set unit test project as startup project, and run the application.
If the function work properly it will gives us Passed result as you see in below diagram.

If the Unit test gives us Failed result it means something wrong in function as you see in the below diagram.

Regards, 

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