Beyond the xUnits themselves , many add-on tools are available that extend the functionality of existing unit test frameworks into specialized domains, rather than acting as standalone tools. A representative set of popular extensions is listed here.
An xUnit extension to support XML testing. Versions exist as extensions to both JUnit and NUnit. This is covered in Chapter 10 of this book.
A JUnit extension that supports writing code performance and scalability tests. It is written in and used with Java.
A JUnit extension for unit testing server-side code such as servlets, JSPs, or EJBs. It is written in and used with Java.
A JUnit extension that supports writing GUI tests for Java Swing applications. It is written in and used with Java.
An NUnit extension that supports GUI tests of Windows Forms applications. It is written in C# and can be used with any .NET language.
An extension to JUnit that tests web-based applications. It simulates a web browser, and is oriented towards writing tests that deal with HTML pages.
Another JUnit extension that tests web-based applications. It is oriented towards writing tests that deal with HTTP request and response objects.
A helpful extension to JUnit that automatically finds and reports code that is not covered by unit tests. Versions exist for Python (Pester) and NUnit (Nester). Many other code coverage tools with similar functionality exist.