Is that a bug that it says 'TESTING PASSED' even though it failed to start Tor? Is the permission denied error because I need to be root to run the tests? If so, how to change the tests so that being root isn't necessary?
Yea, saying 'PASSED' rather than 'FAILED' would be a bug.
No, the tests definitely don't need to be ran as root. Did you clone stem as root? It expects to be able to make a data directory within the test directory.