Steps--> 1.Create a new project in console application. 2.Write the production code in a separate class file.I have written a regular calculator that can do addition, substraction, multiplication, division operation. 3.Add a new class library for test purpose. 4.Add a reference to our production code from our test project. 5.Install NUnit3Test Adapter Tools->Extensions and Updates->Online->NUnit3 Test Adpter 6.Install NUnit Reference->Manage Nuget Packages->Online->Nunit Now we can use NUnit’s attributes and NUnit asserts. 7.Under class library file write the test code using NUnit attributes. [TestFixture] public class RegularCalcultorTests { RegularCalculator calculator; [SetUp] public void BeforeEachTest () { calculator = new RegularCalculator(); } [Test] public void TestAddition () { var...