Introduction

So how to choose our unit test framework? Take a look at this discussion,

NUnit vs. MbUnit vs. MSTest vs. xUnit.net

In this article, we will use MSTest for example, and learn how to use NSubstitute for mocking and decoupling.

Environment

• Visual Studio 2015 Update 3
• .NET Core : 1.0.0
• dotnet-test-mstest : 1.1.2-preview
• MSTest.TestFramework : 1.0.8-rc

Implement

Install packages

1. dotnet-test-mstest
2. MSTest.TestFramework

Unit test sample

[TestClass]
public class UnitTestDemo
{
        [TestMethod]
        public void TestSplitCount()
        {
            var input = "Luke Skywalker, Leia Skywalker, Anakin Skywalker";
            var expected = 3;
            var actual = input.Split(',').Count();
            Assert.AreEqual(expected, actual);
        }
}

• Test result

Using NSubstitute

Assume that we have a class, SplitCounter, which load the separator from configuration file (appsettings.json) as following,

• SplitCounter.cs

public class SplitCounter
    {
        public ISplitConfig _splitConfig = null;

        public SplitCounter()
        {
            this._splitConfig = new SplitConfig();
        }

        public int Calculate(string input)
        {
            if (this._splitConfig == null)
            {
                throw new NullReferenceException("SplitConfig is null!");
            }
            else
            {
                return input.Split(this._splitConfig.Separator).Count();
            }
        }
    }

• ISplitConfig.cs

public interface ISplitConfig
{
        char[] Separator { get; set; }
}

• SplitConfig.cs

public class SplitConfig : ISplitConfig
{
        public char[] Separator { get; set; }

        public SplitConfig()
        {
            var builder = new ConfigurationBuilder()
                .SetBasePath(Directory.GetCurrentDirectory())
                .AddJsonFile("appsettings.json");

            var configuration = builder.Build();

            var separator = configuration["Separator"];
            this.Separator = separator.ToCharArray();
        }
}

• appsettings.json

{
  "Separator": ","
}

However, we don’t want the SplitCounter instance rely on anything from configuration file when unit-testing.

Let us use NSubstitute to mock ISplitConfig instance in SplitCounter.

Install NSubstitute

1. NSubstitute

Unit Test

[TestMethod]
public void TestSplitCounterWithNSub()
{
            #region Create the Substitutes
            var splitConfig = Substitute.For<ISplitConfig>();
            #endregion

            #region Set the return value of the mock objects
            splitConfig.Separator.Returns(new char[] { ';' });
            #endregion

            #region Intialize the test target
            var splitCounter = new SplitCounter();
            splitCounter._splitConfig = splitConfig;
            #endregion


            var input = "Luke Skywalker;Leia Skywalker;AnakinSkywalker";
            var expected = 3;
            var actual = splitCounter.Calculate(input);
            Assert.AreEqual(expected, actual);
}

• Test Result

Reference

1. Announcing MSTest V2 Framework support for .NET Core 1.0 RTM