If you have multiple users that run tests simultaneously on the same machine, you must specify to the mysql-test-run.pl program which ports to use so that no test run conflicts with others running concurrently. You add unique port arguments to mysql-test-run.pl, such as --no-manager --master_port=3911 --slave_port=3927.

Only one person at a time can run the mysql-test-run.pl program in the same mysql-test directory on a shared drive. The mysql-test/var directory created and used by mysql-test-run.pl cannot be shared between simultaneous test runs. A test run can use the --var=dir_path option to specify an alternate directory not used by other runs.