The <filename>mozconfig</filename> above disables the tests because they use a lot more time and disk space for no obvious benefit. If you have nevertheless enabled them, you can run the tests by executing <command>./mach gtest</command>. This will require a network connection, and to be run from within an Xorg session - there is a popup dialog when it fails to connect to ALSA (that does not create a failed test).One or two tests will fail.To see the details of the failure(s) you will need to log the output from that command so that you can review it.