crm.fsf.org/20131203/files/sites/all/modules-new/civicrm/tests/extensions/README.txt

   1 Extensions in the "test.*" namespace are used for testing the extension
   2 system.  All "test.*" extensions are automatically uninstalled in between
   3 test runs.
   4
   5 Note: For simplicity and performance, the automatic uninstallation may
   6 bypass the normal lifecycle events (hook_install, hook_enable, hook_disable,
   7 hook_uninstall); therefore, "test.*" extension should not rely on lifecycle
   8 hooks.