C# NUnit

last modified July 5, 2023

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

NUnit is a unit-testing library for all .NET languages. It was inspired by Java's JUnit. Other unit-testing libraries include XUnit and MSTest.

It is possible to 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 show the latter option.

$ dotnet add Microsoft.NET.Test.Sdk
$ dotnet new nunit
$ dotnet add NUnit3TestAdapter

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

C# NUNit simple example

We start with a simple example.

namespace Arithmetic;
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 test simple arithmetic functions.

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

namespace Testing;
using NUnit.Framework;
using Arithmetic;
class ArithTest
{
 [Test]
 public void SimpleArithmetic()
 {
 int r1 = Basic.add(3, 3);
 Assert.AreEqual(r1, 6);
 int r2 = Basic.sub(3, 3);
 Assert.AreEqual(r2, 0);
 int r3 = Basic.mul(3, 3);
 Assert.AreEqual(r3, 9);
 int r4 = Basic.div(3, 3);
 Assert.AreEqual(r4, 1);
 }
}

The test method is annotated with the [Test] 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: 1, Skipped: 0, Total: 1, ...

C# NUnit skipping tests

Test methods can be skipped with [Ignore] attribute.

namespace Testing;
using NUnit.Framework;
using Arithmetic;
class ArithTest
{
 [Test]
 public void AddSub()
 {
 int r1 = Basic.add(3, 3);
 Assert.AreEqual(r1, 6);
 int r2 = Basic.sub(3, 3);
 Assert.AreEqual(r2, 0);
 }
 [Test]
 [Ignore("Ignoring")]
 public void MulDiv()
 {
 int r3 = Basic.mul(3, 3);
 Assert.AreEqual(r3, 9);
 int r4 = Basic.div(3, 3);
 Assert.AreEqual(r4, 1);
 }
}

We have two test methods. One of them is skipped using the [Ignore] attribute.

C# NUnit TestCase

With TestCase attribute, we can have parameterized test methods.

namespace Testing;
using NUnit.Framework;
using Arithmetic;
class ArithTest
{
 [TestCase(1, 2, 3)]
 [TestCase(2, 2, 4)]
 [TestCase(-1, 4, 3)]
 public void Add(int x, int y, int z)
 {
 int r = Basic.add(x, y);
 Assert.AreEqual(r, z);
 }
 [TestCase(1, 2, -1)]
 [TestCase(2, 2, 0)]
 [TestCase(3, 2, 1)]
 public void Sub(int x, int y, int z)
 {
 int r = Basic.sub(x, y);
 Assert.AreEqual(r, z);
 }
 [TestCase(9, 3, 27)]
 [TestCase(3, 3, 9)]
 [TestCase(-3, -3, 9)]
 public void Mul(int x, int y, int z)
 {
 int r = Basic.mul(x, y);
 Assert.AreEqual(r, z);
 }
 [TestCase(9, 3, 3)]
 [TestCase(3, 3, 1)]
 [TestCase(8, 2, 4)]
 public void Div(int x, int y, int z)
 {
 int r = Basic.div(x, y);
 Assert.AreEqual(r, z);
 }
}

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

C# NUnit TestCaseSource

The [TestCaseSource] attribute allows us to read the data for the parameterized test methods from different sources.

namespace Testing;
using NUnit.Framework;
using Arithmetic;
public class ArithTest
{
 [TestCaseSource(nameof(AddCases))]
 public void Add(int x, int y, int z)
 {
 int r = Basic.add(x, y);
 Assert.AreEqual(r, z);
 }
 [TestCaseSource(nameof(SubCases))]
 public void Sub(int x, int y, int z)
 {
 int r = Basic.sub(x, y);
 Assert.AreEqual(r, z);
 }
 [TestCaseSource(nameof(MulCases))]
 public void Mul(int x, int y, int z)
 {
 int r = Basic.mul(x, y);
 Assert.AreEqual(r, z);
 }
 [TestCaseSource(nameof(DivCases))]
 public void Div(int x, int y, int z)
 {
 int r = Basic.div(x, y);
 Assert.AreEqual(r, z);
 }
 static object[] AddCases =
 {
 new object[] { 1, 2, 3 },
 new object[] { 2, 2, 4 },
 new object[] { -1, 4, 3 }
 };
 
 static object[] SubCases =
 {
 new object[] { 1, 2, -1 },
 new object[] { 2, 2, 0 },
 new object[] { 3, 2, 1 }
 };
 static object[] MulCases =
 {
 new object[] { 9, 3, 27 },
 new object[] { 3, 3, 9 },
 new object[] { -3, -3, 9 }
 };
 static object[] DivCases =
 {
 new object[] { 9, 3, 3 },
 new object[] { 3, 3, 1 },
 new object[] { 8, 2, 4 }
 };
}

In this example, the values are placed in arrays.

C# NUnit ExpectedResult

With ExpectedResult, we can simplify our test setup.

namespace Testing;
using NUnit.Framework;
using Arithmetic;
class ArithTest
{
 [TestCase(1, 2, ExpectedResult = 3)]
 [TestCase(2, 2, ExpectedResult = 4)]
 [TestCase(-1, 4, ExpectedResult = 3)]
 public int Add(int x, int y)
 {
 return Basic.add(x, y);
 }
 [TestCase(1, 2, ExpectedResult = -1)]
 [TestCase(2, 2, ExpectedResult = 0)]
 [TestCase(3, 2, ExpectedResult = 1)]
 public int Sub(int x, int y)
 {
 return Basic.sub(x, y);
 }
 [TestCase(9, 3, ExpectedResult = 27)]
 [TestCase(3, 3, ExpectedResult = 9)]
 [TestCase(-3, -3, ExpectedResult = 9)]
 public int Mul(int x, int y)
 {
 return Basic.mul(x, y);
 }
 [TestCase(9, 3, ExpectedResult = 3)]
 [TestCase(3, 3, ExpectedResult = 1)]
 [TestCase(8, 2, ExpectedResult = 4)]
 public int Div(int x, int y)
 {
 return Basic.div(x, y);
 }
}

With ExpectedResult, our code is shortened a bit.

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.

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 add nunit
$ dotnet add reference ..\PalindromeService\PalindromeService.csproj

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

<Project Sdk="Microsoft.NET.Sdk">
 <PropertyGroup>
 <TargetFramework>net6.0</TargetFramework>
 <Nullable>enable</Nullable>
 <IsPackable>false</IsPackable>
 </PropertyGroup>
 <ItemGroup>
 <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.1.0" />
 <PackageReference Include="nunit" Version="3.13.3" />
 <PackageReference Include="NUnit3TestAdapter" Version="4.2.1" />
 <PackageReference Include="coverlet.collector" Version="3.1.0" />
 </ItemGroup>
 <ItemGroup>
 <ProjectReference Include="..\PalindromeService\PalindromeService.csproj" />
 </ItemGroup>
</Project>

This is how the project file looks like.

namespace Palindrome.Services.Tests;
using NUnit.Framework;
public class Tests
{
 private PalindromeService? _palindromeService;
 [SetUp]
 public void SetUp()
 {
 _palindromeService = new PalindromeService();
 }
 [TestCase("racecar")]
 [TestCase("nun")]
 [TestCase("level")]
 public void IsPalindrome(string word)
 {
 var r = _palindromeService!.IsPalindrome(word);
 Assert.AreEqual(r, true);
 }
}

We test the IsPalindrome method with three words.

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

The [Setup] 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 NUnit and .NET Core

In this article we have done unit testing in C# with NUnit 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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