Currently trunk uses the default derby.locks.waitTimeout (60) and a derby.locks.deadlockTimeout of 5. I suspect that these can be tuned for the developer's hardware and provide quicker test execution.
setting waitTimeout = 10 saved me 5 - 10 minutes on a build last night.
The properties can be specified on the command line :
$ mvn -Dderby.locks.deadlockTimeout=10 -Dderby.locks.waitTimeout=15 clean test
or in settings.xml :
The profile (as shown) needs to be activated on the command line :
$ mvn -Pderby-locking clean test