Clover

Clover Coverage Report

The "phpunit" target - when configured accordingly and when XDebug is enabled on the build machine - generates an xml-file containing all lines of code that were executed during the unit tests. This coverage can help to organize efforts to get things under test.
 
Here's how to set up the report.
Prerequisite is, that your build includes the "phpunit" target, which writes a file build/logs/clover.xml
For the HTML-Report, the ILIAS build is set up to write it to build/coverage.

There are two reports. The first one is the overview report:

You can also link a generic HTML - Report to the directory. you will get the following detail report:

Using this, you can browse through the code. From everywhere, you can access the dashboard that looks like this:

12 Apr 2014 MB: The metric Change Risk AntiPattern or CRAP is explained in the subchapter "Software Metrics Explained".
Please keep in mind, that all metrics considering phpunit-coverage do not take into account the - at the time of this writing - thousands of files which are not under test.