tests: installed tests should use TAP
tests: installed tests should use TAP

The GNOME installed tests system expects the test output to be TAP:

"The key Output (if specified) can only take one value at present, which is TAP. This specifies that the test outputs Test Anything Protocol."
(https://wiki.gnome.org/Initiatives/GnomeGoals/InstalledTests)

Export MUTEST_OUTPUT=tap so this is the case.

ebassi/graphene,ebassi/graphene