Command-line utility to test concurrent writes do not corrupt files?

Command-line utility to test concurrent writes do not corrupt files?

Is there a command-line utility that can test concurrent writes by
different processes to a file does not corrupt it? (i.e. general purpose
testing tool to test effectiveness of POSIX locks, etc.)
I'm more interested in one for Linux at the moment, but if you can provide
one(s) that work in other *nix and/or Windows, that would help.