Information The custom PHPUnit test suite used later in the testing instructions has been created with the following command. Putting it here for future reference. Just replace HEAD with any commit and it will generate the test suite for you. echo '<testsuite name="MDL-xxxx">' && \ git show --pretty="" --name-only HEAD | \ grep "/tests/.*_test.php" | \ xargs -I{} echo " <file>{}</file>" && \ echo "</testsuite>" Running tests Init PHPUnit ( php admin/tool/phpunit/cli/init.php ). Edit the generated phpunit.xml Immediately after the <testsuites> line paste the contents of the attached custom_testsuite.txt file, that has been generated with the information above. Verify that the number of files in the custom testsuite matches the number of test files modified by the patch (right now, 53). Ensure that you have PCOV or XDEBUG installed and enabled in your site. Run the following phpunit command (note it can take really long): vendor/bin/phpunit -v --coverage-html /tmp/cc --testsuite MDL-xxxx Verify the the first lines of the execution confirm that you're using PCOV or XDEBUG for coverage calculations. If that's missing it means that none of them are available. Verify that there isn't any "covers warning" once the test ends. Note that there can be skipped tests, and also failed tests, but the important detail here is that, when running the test with code-coverage enabled, there aren't warnings any more. Verify that in the /tmp/cc directory has contents and that, if you open the index.html file in you browser you can see and navigate over coverage results.