Microsoft VisualStudio Unit Testing method should be decorated with a [TestMethod] attribute.

[TestMethod]
public void TestAddMethod()
{
        

}

Microsoft VisualStudio Unit Testing class should be declared with a [TestClass] attribute

 [TestClass]
    public class UnitTestMath
    {
        [TestMethod]
        public void TestAdd()
        {
        }
    }

Namespace used for Microsoft Visual Studio Unit Testing –Microsoft.VisualStudio.TestTools.UnitTesting

Example in C# :

using System;
using System.Text;
using System.Collections.Generic;
using System.Linq;
using Microsoft.VisualStudio.TestTools.UnitTesting;
namespace TestProjectMath
{
  
    [TestClass]
    public class UnitTestMath
    {
     }
}