C# MSTest

C# MSTest tutorial shows how to do unit testing in C# with MSTest framework. Unit testing is a software testing where individual units of a software are tested.

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Aug 29, 2025

C# MSTest

last modified July 5, 2023

C# MSTest tutorial shows how to do unit testing in C# with MSTest framework.

Unit testing is a software testing where individual units (components) of a software are tested. The purpose of unit testing is to validate that each unit of the software performs as designed. A unit is the smallest testable part of any software.

MSTest is a unit-testing library from Microsoft. It is available for all .NET languages. There are other unit-testing libraries including XUnit and NUnit.

We can either place tests in the same project directory or inside a different directory. We start with a simpler option and place tests in the same project directory. In the end, we place tests in a different directory within a solution.

$ dotnet add package Microsoft.NET.Test.Sdk $ dotnet add package MSTest.TestAdapter $ dotnet add package MSTest.TestFramework

In order to use MSTest, we need to add these three libraries.

C# MSTest simple example

We start with a simple example.

Arith.cs

namespace Messages.Services;

public class Messages { public static Func<string> msg1 = () => “Hello there!”; public static Func<string> msg2 = () => “Good Morning!”; }

We test simple message functions.

We put our tests into the tests directory. MSTest automatically discovers our tests.

tests/MessageTest.cs

namespace Messages.Tests;

using Microsoft.VisualStudio.TestTools.UnitTesting; using Messages.Services;

[TestClass] public class MessageTest { private const string Expected1 = “Hello there!”; private const string Expected2 = “Good Morning!”;

[TestMethod]
public void Message1()
{
    var m1 = Messages.msg1();

    Assert.AreEqual(Expected1, m1);
}

[TestMethod]
public void Message2()
{
    var m2 = Messages.msg2();

    Assert.AreEqual(Expected2, m2);
}

}

The class is annotated with the [TestClass] attribute, the test methods are annotated with the [TestMethod] attribute. We use assertions to ensure the correct output.

$ dotnet test … Starting test execution, please wait… A total of 1 test files matched the specified pattern.

Passed! - Failed: 0, Passed: 2, Skipped: 0, Total: 2, …

C# MSTest parameterized tests

The [DataTestMethod] attribute indicates a parameterized method. The parameters are added with the [DataRow] attribute.

Arith.cs

namespace Arithmetic.Services;

public class Basic { public static Func<int, int, int> add = (a, b) => a + b; public static Func<int, int, int> mul = (a, b) => a * b; public static Func<int, int, int> sub = (a, b) => a - b; public static Func<int, int, int> div = (a, b) => a / b; }

We are going to test simple arithmetic functions.

tests/ArithTest.cs

namespace Messages.Tests;

using Microsoft.VisualStudio.TestTools.UnitTesting; using Arithmetic.Services;

[TestClass] public class ArithTest { [DataTestMethod] [DataRow(1, 2, 3)] [DataRow(2, 2, 4)] [DataRow(-1, 4, 3)] public void Add(int x, int y, int expected) { int r = Basic.add(x, y); Assert.AreEqual(r, expected); }

[DataTestMethod]
[DataRow(1, 2, -1)]
[DataRow(2, 2, 0)]
[DataRow(3, 2, 1)]
public void Sub(int x, int y, int expected)
{
    int r = Basic.sub(x, y);
    Assert.AreEqual(r, expected);
}

[DataTestMethod]
[DataRow(9, 3, 27)]
[DataRow(3, 3, 9)]
[DataRow(-3, -3, 9)]
public void Mul(int x, int y, int expected)
{
    int r = Basic.mul(x, y);
    Assert.AreEqual(r, expected);
}

[DataTestMethod]
[DataRow(9, 3, 3)]
[DataRow(3, 3, 1)]
[DataRow(8, 2, 4)]
public void Div(int x, int y, int expected)
{
    int r = Basic.div(x, y);
    Assert.AreEqual(r, expected);
}

}

In this example, we test each method with three sets of values.

[DataTestMethod] [DataRow(1, 2, 3)] [DataRow(2, 2, 4)] [DataRow(-1, 4, 3)] public void Add(int x, int y, int expected) { int r = Basic.add(x, y); Assert.AreEqual(r, expected); }

We are testing the Add method. The method is tested with three sets of values given by the [DataRow] attribute. The calculated and expected values are compared with Assert.AreEqual assertion.

C# MSTest skipping tests

Test methods can be skipped with [Ignore] attribute.

tests/ArithTest.cs

namespace Arithmetic.Tests;

using Microsoft.VisualStudio.TestTools.UnitTesting; using Arithmetic.Services;

[TestClass] public class ArithTest { [DataRow(1, 2, 3)] [DataRow(2, 2, 4)] [DataRow(-1, 4, 3)] [DataTestMethod] public void Add(int x, int y, int z) { int r = Basic.add(x, y); Assert.AreEqual(r, z); }

[DataTestMethod]
[DataRow(1, 2, -1)]
[DataRow(2, 2, 0)]
[DataRow(3, 2, 1)]
public void Sub(int x, int y, int z)
{
    int r = Basic.sub(x, y);
    Assert.AreEqual(r, z);
}

[DataTestMethod]
[DataRow(9, 3, 27)]
[DataRow(3, 3, 9)]
[DataRow(-3, -3, 9)]
[Ignore]
public void Mul(int x, int y, int z)
{
    int r = Basic.mul(x, y);
    Assert.AreEqual(r, z);
}

[DataTestMethod]
[DataRow(9, 3, 3)]
[DataRow(3, 3, 1)]
[DataRow(8, 2, 4)]
[Ignore]
public void Div(int x, int y, int z)
{
    int r = Basic.div(x, y);
    Assert.AreEqual(r, z);
}

}

We have four test methods. Two of them are skipped using the [Ignore] attribute.

$ dotnet test … Starting test execution, please wait… A total of 1 test files matched the specified pattern. Skipped Mul (9,3,27) Skipped Mul (3,3,9) Skipped Mul (-3,-3,9) Skipped Div (9,3,3) Skipped Div (3,3,1) Skipped Div (8,2,4)

Passed! - Failed: 0, Passed: 6, Skipped: 6, Total: 12, Duration: 84 ms …

C# MSTest DynamicData

With [DynamicData] attribute, we can externalize the test data into a method or a property.

tests/ArithTest.cs

namespace Messages.Tests;

using Microsoft.VisualStudio.TestTools.UnitTesting; using Arithmetic.Services;

[TestClass] public class Tests { [DataTestMethod] [DynamicData(nameof(AddData), DynamicDataSourceType.Method)] public void Add(int x, int y, int expected) { int r = Basic.add(x, y); Assert.AreEqual(r, expected); }

[DataTestMethod]
[DynamicData(nameof(SubData), DynamicDataSourceType.Method)]
public void Sub(int x, int y, int expected)
{
    int r = Basic.sub(x, y);
    Assert.AreEqual(r, expected);
}

[DataTestMethod]
[DynamicData(nameof(MulData), DynamicDataSourceType.Method)]
public void Mul(int x, int y, int expected)
{
    int r = Basic.mul(x, y);
    Assert.AreEqual(r, expected);
}

[DataTestMethod]
[DynamicData(nameof(DivData), DynamicDataSourceType.Method)]
public void Div(int x, int y, int expected)
{
    int r = Basic.div(x, y);
    Assert.AreEqual(r, expected);
}

private static IEnumerable&lt;object[]&gt; AddData()
{
    return new[]
    {
        new object[] { 1, 2, 3 },
        new object[] { 2, 2, 4 },
        new object[] { -1, 4, 3 }
    };
}

private static IEnumerable&lt;object[]&gt; SubData()
{
    return new[]
    {
        new object[] { 1, 2, -1 },
        new object[] { 2, 2, 0 },
        new object[] { 3, 2, 1 }
    };
}

private static IEnumerable&lt;object[]&gt; MulData()
{
    return new[]
    {
        new object[] { 9, 3, 27 },
        new object[] { 3, 3, 9 },
        new object[] { -3, -3, 9 }
    };
}

private static IEnumerable&lt;object[]&gt; DivData()
{
    return new[]
    {
        new object[] { 9, 3, 3 },
        new object[] { 3, 3, 1 },
        new object[] { 8, 2, 4 }
    };
}

}

In the example, we have test data in separate methods.

Placing tests in separate directory

In the following example, we show how to place tests in a separate directory.

$ mkdir Separate $ cd Separate

We create a new directory.

$ dotnet new sln

We create a new empty solution.

$ mkdir PalindromeService PalindromeService.Tests

Two directories are created.

$ cd PalindromeService $ dotnet new classlib

We create a new library.

PalindromeService\PalindromeService.cs

namespace Palindrome.Services;

using System.Globalization;

public class PalindromeService { public bool IsPalindrome(string word) { IEnumerable<string> GraphemeClusters(string s) { var enumerator = StringInfo.GetTextElementEnumerator(s); while (enumerator.MoveNext()) { yield return (string)enumerator.Current; } }

    var reversed = string.Join("", GraphemeClusters(word).Reverse().ToArray());

    return reversed == word;
}

}

The PalindromeService contains the IsPalindrome method, which determines if a words is a palindrome.

$ cd .. $ dotnet sln add PalindromeService\PalindromeService.csproj

We add the PalindromeService to the solution.

$ cd PalindromeService.Tests $ dotnet new mstest $ dotnet add reference ..\PalindromeService\PalindromeService.csproj

We go to the PalindromeService.Tests directory and add the unit libraries add the reference to the PalindromeService.

PalindromeService.Tests\PalindromeService.Tests.csproj

<PropertyGroup> <TargetFramework>net6.0</TargetFramework> <Nullable>enable</Nullable>

&lt;IsPackable&gt;false&lt;/IsPackable&gt;

</PropertyGroup>

This is how the project file looks like.

PalindromeService.Tests\Tests.cs

namespace Palindrome.Services.Tests;

using Microsoft.VisualStudio.TestTools.UnitTesting;

[TestClass] public class Tests { private PalindromeService? _palindromeService;

[TestInitialize]
public void SetUp()
{
    _palindromeService = new PalindromeService();
}

[DataTestMethod]
[DataRow("racecar")]
[DataRow("level")]
[DataRow("nun")]
public void IsPalindrome(string word)
{
    var r = _palindromeService!.IsPalindrome(word);
    Assert.AreEqual(r, true);
}

}

We test the IsPalindrome method with three words.

[TestInitialize] public void SetUp() { _palindromeService = new PalindromeService(); }

The [TestInitialize] attribute is used to provide a common set of functions that are performed just before each test method is called. In our case, we create the PalindromeService.

$ cd .. $ dotnet sln add PalindromeService.Tests\PalindromeService.Tests.csproj

We add the test project to the solution.

$ dotnet test

Finally, we can run the tests.

Source

Unit testing C# with MSTest and .NET

In this article we have done unit testing in C# with MSTest library.

Author

My name is Jan Bodnar, and I am a passionate programmer with extensive programming experience. I have been writing programming articles since 2007. To date, I have authored over 1,400 articles and 8 e-books. I possess more than ten years of experience in teaching programming.

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