Please explain JUnit extensions?

There are four extensions of Junit-

• XML Unit
• MockObject
• Cactus
• JWebUnit

• XML Unit- It offers a set of supporting classes, a single JUnit extension class, XMLTestCase allowing the assertions to be made about the validity of a piece of XML, individual nodes in an XML piece which DOM Traversal exposes and many more.
• MockObject- This extension is used for the simulation of the behavior of the real and complex objects which are useful in the incorporation of the unit test.
• Cactus- For lowering the cost of writing the tests and the server-side code, the simple test framework is used. It extends the JUnit and executes an in-container strategy which results in the execution of testing inside a container. Cactus Integration Modules and Cactus Framework are the important components of Cactus.
• JWebUnit- This extension has a simple and unified testing interface wrapping the existing frameworks such as Selenium, and HtmUnit. Navigation of the web applications is done with a set of assertions by this high-level Java API.