It allows you to run all of the following: all core testcases at once, all core test groups, each core test case individually, all application-specific testcases at once, all application-specific test groups and each core test case individually. It also supports plugins, which means you can run plugin cases and groups.

He includes some samples of how it works - a few command line calls and what the output looks like.

For a testing framework I picked PHPUnit. My main reason for picking this was that its fully written in PHP5, it can produce some pretty good reports and the biggest reason is simply because I hear a lot of good stuff about it.

Among his thoughts were mentions of PHPUnit's great documentation (but made it hard to just get started), a bit of unintuitive functionality with the addTestSuite method and some of the pain that it took to get together a full suite of tests.