Mockery : Mockery is a simple yet flexible PHP mock object framework for use in unit testing with PHPUnit, PHPSpec or any other testing framework. Its core goal...
PHPUnit : PHPUnit is the de-facto standard for unit testing in PHP projects. It provides both a framework that makes the writing of tests easy as well as the fu...
PHP unified diff patcher : A powerful class which allows to create and merge unified diff patches into any file. Fully written in PHP, uses the GNU standard unified diff format ...
Pimple : Pimple is a small Dependency Injection Container for PHP 5.3 that consists of just one file and one class (about 50 lines of code).
vfsStream is a stream wrapper for a virtual file system that may be helpful in unit tests to mock the real file system. It can be used with any unit test framework, like PHPUnit or SimpleTest.