Intro

An example of how to use NUnit by creating a unit test project manually.

There is a Visual Studio extension (Test Generator NUnit extension) that automates the creation of a unit test project, following some standard naming conventions.

Documentation

Introduction To NUnit Testing Framework - Has a good step-by-step example using Visual Studio.
Unit testing C# with NUnit and .NET Core - A tutorial on unit testing - Example using dotnet CLI.

Creating Unit Test Project - aka Test Runner

Create a solution and application code as shown here: .NET CLI
Unit Tests should always go in a separate directory from the class directory so create a PrimeService.Tests directory

PS C:\Users\Roger\source\repos\LearningDotNet\NUnit> mkdir PrimeService.Tests

    Directory: C:\Users\Roger\source\repos\LearningDotNet\NUnit
Mode                 LastWriteTime         Length Name
----                 -------------         ------ ----
d-----         1/17/2021  12:30 AM                PrimeService.Tests

PS C:\Users\Roger\source\repos\LearningDotNet\NUnit> dir
    Directory: C:\Users\Roger\source\repos\LearningDotNet\NUnit

Mode                 LastWriteTime         Length Name
----                 -------------         ------ ----
d-----         1/17/2021  12:15 AM                PrimeService
d-----         1/17/2021  12:30 AM                PrimeService.Tests
-a----         1/17/2021  12:16 AM           1743 NUnit.sln

Change to PrimeService.Tests directory and create the project file with the NUnit template: dotnet new nunit
This steps adds all the external dependencies and also automatically downloads them from a nuget repository via: dotnet restore

PS C:\Users\Roger\source\repos\LearningDotNet\NUnit\PrimeService.Tests> dotnet new nunit
The template "NUnit 3 Test Project" was created successfully.

Processing post-creation actions...
Running 'dotnet restore' on C:\Users\Roger\source\repos\LearningDotNet\NUnit\PrimeService.Tests\PrimeService.Tests.csproj...
  Restoring packages for C:\Users\Roger\source\repos\LearningDotNet\NUnit\PrimeService.Tests\PrimeService.Tests.csproj...
  Installing System.Diagnostics.TextWriterTraceListener 4.0.0.
  Installing System.ComponentModel.EventBasedAsync 4.0.11.
  Installing Microsoft.DotNet.PlatformAbstractions 1.0.3.
  Installing Microsoft.TestPlatform.ObjectModel 15.7.2.
  Installing Microsoft.Extensions.DependencyModel 1.0.3.
  Installing Microsoft.TestPlatform.TestHost 15.7.2.
  Installing Microsoft.CodeCoverage 1.0.3.
  Installing System.Xml.XPath.XmlDocument 4.3.0.
  Installing System.ComponentModel.EventBasedAsync 4.3.0.
  Installing Microsoft.NET.Test.Sdk 15.7.2.
  Installing NUnit3TestAdapter 3.10.0.
  Installing NUnit 3.10.1.
  Generating MSBuild file C:\Users\Roger\source\repos\LearningDotNet\NUnit\PrimeService.Tests\obj\PrimeService.Tests.csproj.nuget.g.props.
  Generating MSBuild file C:\Users\Roger\source\repos\LearningDotNet\NUnit\PrimeService.Tests\obj\PrimeService.Tests.csproj.nuget.g.targets.
  Restore completed in 4.82 sec for C:\Users\Roger\source\repos\LearningDotNet\NUnit\PrimeService.Tests\PrimeService.Tests.csproj.

Restore succeeded.

Now, add the PrimeService class library as another dependency to the project. Use the dotnet add reference

PS C:\Users\Roger\source\repos\LearningDotNet\NUnit\PrimeService.Tests> dotnet add reference ../PrimeService/PrimeService.csproj
Reference `..\PrimeService\PrimeService.csproj` added to the project.

Add the unit tests project to the solution.

You can now use the solution with Visual Studio

Creating A Test Case

Now that you have a solution created with a template for doing unit tests, it is time to add tests.

In the PrimeService.Tests directory, rename the UnitTest1.cs file to PrimeService_IsPrimeShould.cs and replace its entire contents with the following code:

The [TestFixture] attribute denotes a class that contains unit tests. The [Test] attribute indicates a method is a test method.

Executing Tests

To build the library and execute the test, use: dotnet test

For some reason I couldn’t figure out, the test executor decided to look for tests in the PrimeService.dll. The test does run when it executes against PrimeService.Tests. We expect the test to fail since we haven’t written any code in our library.

Add Code To Library

Change IsPrime to deal with input == 1.

Specifiy the test directory to avoid running tests against the library project.

Test Cases

A [TestCase] attribute is used to create a suite of tests that execute the same code but have different input arguments. You can use the [TestCase] attribute to specify values for those inputs.

Run Tests From Studio

You can run the NUnit tests from the Test menu.

Languages

Using NUnit Example