JUnit is described as 'unit testing framework for the Java programming language. JUnit has been important in the development of test-driven development, and is one of a family of unit testing frameworks collectively known as xUnit that originated with SUnit'. There are three alternatives to JUnit for Windows, Linux and Mac. The best alternative is TestNG, which is free. Other great apps like JUnit are NUnit (Free, Open Source) and XUnit (Free, Open Source).
NUnit is a unit-testing framework for all .Net languages. Initially ported from JUnit, the current production release, version 2.5, is the sixth major release of this xUnit based unit testing tool for Microsoft .NET.
xUnit.net is a developer testing framework, built to support Test Driven Development, with a design goal of extreme simplicity and alignment with framework features. It is compatible with .NET Framework 2.