Create a Unit Test Case in C# using Moq

In this post we are going to see how to create a unit test case in C# using Moq. First we create a library project and write the following code.

public interface ICalculator

    {

       (string operation, int result) DoOperation(string operation, int a, int b);

    }

    public class Calculator:ICalculator

    {

        public (string operation,int result) DoOperation(string operation,int a,int b)

        {

            (string operation, int result) operationResult;

            int c = 0;

            switch (operation)

            {

                case "add":

                    c = a + b;

                    break;

                case "sub":

                    c = a - b;

                    break;

                case "mul":

                    c = a * b;

                    break;

                default:

                    c = a + b;

                    break;

            }

            operationResult =(operation, c);

            return operationResult;

        }

    }

public class CalMachine

    {

        private ICalculator calc;

        public CalMachine():this(new Calculator())

        {

        }

        public CalMachine(ICalculator obj)

        {

            this.calc = obj;

        }

       public (string operation, int result) Operate(string operationType, int a , int b)

        {

            return calc.DoOperation(operationType, a, b);

        }

    }

Now create a unit test case project and add the reference of library project to the unit test case project
Then install the Moq using nuget package manager. Mock the interface and pass that object to the instance. Then setup the method DoOperation, where the method mock and returns the response which has mentioned in the Returns

[TestClass]

    public class UnitTest1

    {

        [TestMethod]

        public void TestMethod1()

        {

            // Arrange

            Moq.Mock<ICalculator> cal = new Moq.Mock<ICalculator>();

         cal.Setup(x => x.DoOperation(It.IsAny<string>(), It.IsAny<int>(), It.IsAny<int>()))                                        .Returns(("add", 3));

            CalMachine machine = new CalMachine(cal.Object);

            // ACT

            (string operation, int result) result = machine.Operate("add", 1, 3);

            // Assert

            Assert.AreEqual("add", result.operation);

            Assert.AreEqual(3, result.result);

        }

    }

From this code you can learn how to write a unit test case for c# project using Moq.