This test is aimed at stressing the fcntl locking functions.

A master process sets a lock on a file region (byte range locking).
Several slave processes try to perform operations on this region,
such as: read, write, set a new lock ... The expected results of
these operations are known. If the operation's result is the same
as the expected one, the test succeeds, otherwise it fails.

Locktests stress POSIX locks.