PHPUnit_Framework_Exception

Base class for all PHPUnit Framework exceptions.

Ensures that exceptions thrown during a test run do not leave stray references behind.

Every Exception contains a stack trace. Each stack frame contains the 'args' of the called function. The function arguments can contain references to instantiated objects. The references prevent the objects from being destructed (until test results are eventually printed), so memory cannot be freed up.

With enabled process isolation, test results are serialized in the child process and unserialized in the parent process. The stack trace of Exceptions may contain objects that cannot be serialized or unserialized (e.g., PDO connections). Unserializing user-space objects from the child process into the parent would break the intended encapsulation of process isolation.