Here's what I'm doing:

./gjs-unit -p /js/GObjectClass

/js/GObjectClass:       JS LOG: running test testDerived
   JS MEMORY: Memory report: before destroying context
   JS MEMORY:   95 objects currently alive
   JS MEMORY:            boxed = 4
   JS MEMORY:           gerror = 0
   JS MEMORY:          closure = 2
   JS MEMORY:         database = 0
   JS MEMORY:         function = 67
   JS MEMORY:         importer = 2
   JS MEMORY:               ns = 4
   JS MEMORY:           object = 11
   JS MEMORY:            param = 3
   JS MEMORY:             repo = 1
   JS MEMORY:        resultset = 0
   JS MEMORY:         weakhash = 0
   JS MEMORY:        interface = 1
   JS MEMORY: Memory report: after destroying context
   JS MEMORY:   2 objects currently alive
   JS MEMORY:            boxed = 0
   JS MEMORY:           gerror = 0
   JS MEMORY:          closure = 2
   JS MEMORY:         database = 0
   JS MEMORY:         function = 0
   JS MEMORY:         importer = 0
   JS MEMORY:               ns = 0
   JS MEMORY:           object = 0
   JS MEMORY:            param = 0
   JS MEMORY:             repo = 0
   JS MEMORY:        resultset = 0
   JS MEMORY:         weakhash = 0
   JS MEMORY:        interface = 0

** (/data/projects/gjs/.libs/gjs-unit:25274): ERROR **: after destroying context: JavaScript objects were leaked.

FWIW, commenting out all other tests in testGObjectClass.js still results in the above error.