Writing unit tests can be hard and sometimes good design has to be sacrificed for the sole purpose of testability. Often testability corresponds to good design, but this is not always the case. For example final classes and methods cannot be used, private methods sometimes need to be protected or unnecessarily moved to a collaborator, static methods should be avoided completely and so on simply because of the limitations of existing frameworks.
PowerMock is a framework that extend other mock libraries such as EasyMock with more powerful capabilities. PowerMock uses a custom classloader and bytecode manipulation to enable mocking of static methods, constructors, final classes and methods, private methods, removal of static initializers and more. By using a custom classloader no changes need to be done to the IDE or continuous integration servers which simplifies adoption. Developers familiar with EasyMock will find PowerMock easy to use, since the entire expectation API is the same, both for static methods and constructors. PowerMock extends the EasyMock API with a small number of methods and annotations to enable the extra features. From version 1.1 PowerMock also has basic support for Mockito.
When writing unit tests it is often useful to bypass encapsulation and therefore PowerMock includes several features that simplifies reflection specifically useful for testing. This allows easy access to internal state, but also simplifies partial and private mocking.
p-unit
An open source framework for unit test and performance benchmark, which was initiated by Andrew Zhang, under Apache License v2.0. p-unit supports to run the same tests with single thread or multi-threads, tracks memory and time consumption, and generates the result in the form of plain text, image or pdf file.
ClassMock is a framework that helps the creation of unit tests for components that use reflection or annotations. In this kind of classes, the behavior is dependent of the class structure. This way, each test case usually works with a different class created specifically for the test. With ClassMock is possible to define and generate classes in runtime, allowing a better test readability and logic sharing between tests.
FEST-Assert is a Java library that provides a fluent interface for writing assertions. Its main goal is to improve test code readability and make maintenance of tests easier.
FEST-Assert requires Java SE 5.0 or later and can be used with either JUnit or TestNG.