At some point, many php developers turn to the pcntl functions in php to write a daemon, or server, or simulate threading. But how do you unit test this with complete code coverage? [...] We need to engage some black arts php extensions to make this happen. An installation guide follows, and the post ends with a complete listing of the unit test.

He uses the test_helpers extension (as provided by Sebastian Bergmann) and Runkit to allow the test to define new methods copying the current pcntl methods and mocks up the responses. Tests are included to check the parent of a process, checking the children of a process and testing that a fork could be made. Hes's even included visual proof of this working.