For most .NET developers, running tests has long appeared simple: add MSTest, NUnit, or xUnit.net, write a few test methods, and run dotnet test . Under that command, however, sits a test platform responsible for discovering tests, loading adapters, starting processes, collecting results, and integrating with editors and CI systems.

That distinction matters:

A test framework defines how tests are written. Examples include MSTest, NUnit, xUnit.net, and TUnit.

A test platform discovers and executes those tests and connects them to command-line tools, IDEs, and build pipelines.

For many years, VSTest was the standard platform behind .NET testing. Microsoft.Testing.Platform (MTP) is its modern, lightweight alternative. It does not replace test frameworks; instead, it changes how their tests are hosted and executed.

How .NET testing reached this point

The earliest .NET test runners were closely associated with their frameworks or development environments.…