Moq - Unit Test In .NET Core App Using Mock Object

using MVCproject.Core;

namespace MVCproject.Infrastructure
{
    public class EmployeeRepository : IGetDataRepository
    {
        public string GetNameById(int id)
        {
            string name;
            if (id == 1)
            {
                name = "Jignesh";
            }
            else if (id == 2)
            {
                name = "Rakesh";
            }
            else
            {
                name = "Not Found";
            }
            return name;
        }
    }
}

MVCProject\Controllers\HomeController.cs

using Microsoft.AspNetCore.Mvc;
using MVCproject.Core;

namespace MVCProject.Controllers
{
    public class HomeController : Controller
    {
        private readonly IGetDataRepository _data;

        public HomeController(IGetDataRepository data)
        {
            _data = data;
        }

        public IActionResult Index()
        {
            return View();
        }

        public string GetNameById(int id)
        {
            return _data.GetNameById(id);
        }
    }
}

Here, to create a controller class instance, we require the object of IGetDataRepository. Without a mock object, we need to create an object of IGetDataRepository which is real.

Moq library allows us to manipulate the mock object in many ways, such as setting mock methods to return specific values, setting up required properties, and matching the specific arguments when test method is called mock object.

Moq can create a mock version of IGetDataRepository. To demonstrate the code, I am using the MSTest framework. In this example, I am using the Setup and Returns methods to create a mock object. The Setup method is used to tell the mock object how to behave when it calls for a test method and return methods return a specific value.

MockingUnitTest\MSTestProject\UnitTest1.cs

using Microsoft.VisualStudio.TestTools.UnitTesting;
using MVCProject.Controllers;
using Moq;
using Microsoft.Extensions.Logging;
using MVCproject.Core;
using MVCproject.Controllers;

namespace TestProject
{
    [TestClass]
    public class UnitTest1
    {
        [TestMethod]
        public void TestMethod2()
        {
            var mock = new Mock<IGetDataRepository>();
            mock.Setup(p => p.GetNameById(1)).Returns("Jignesh");
            HomeController home = new HomeController(mock.Object);
            string result = home.GetNameById(1);
            Assert.AreEqual("Jignesh", result);
        }
    }
}

The Moq library is rge same for all the unit test framework. It means that the above test will work with XUnit and NUnit after some syntax modification.

Summary

The Unit test is code where we test all the code paths of the methods and ensure that the results are as expected. A mock object is an object that can act as a real object but can be controlled in test code. It is very useful in generating the objects that are used in the test method.

You can view or download the source code from here.