PASS Lock request with ifAvailable - lock available
PASS Lock request with ifAvailable - lock not available
PASS Lock request with ifAvailable - lock not available, callback throws
PASS Lock request with ifAvailable - unrelated lock held
PASS Shared lock request with ifAvailable - shared lock held
PASS Exclusive lock request with ifAvailable - shared lock held
PASS Shared lock request with ifAvailable - exclusive lock held
PASS Returned Promise rejects if callback throws synchronously
PASS Returned Promise rejects if async callback yields rejected promise
PASS Locks are available once previous release is processed