I noticed that PhabricatorLibraryTestCase::testMethodVisibility takes a long time to execute (up to 90 seconds on my laptop). Looking at the profile it seems that most (54.5%) of the execution time is spent in PhutilLibraryTestCase::getVisibility. Rewriting PhutilLibraryTestCase::testMethodVisibility to use a bitmask instead of strings seems to provide a significant performance improvement (on my local machine, this test now takes 45 seconds, see the profile).

arc unit