How do I set up NUnit in Visual Studio 2022?
You can add both NUnit Framework and NUnit Test Adapter using NuGet Packages. To do that, right click on your project in Solution Explorer, go to Manage NuGet packages…, in the Browse section type nunit, install NUnit package and the corresponding version adapter (NUnitTestAdapter for NUnit 2.x or NUnit3TestAdapter for NUnit 3.x).