Within a test case, many system variables can be set by using statements such as these:

SET sql_warnings=1;
SET sql_mode='NO_AUTO_VALUE_ON_ZERO';

But sometimes you need to restart the server to use command-line options that are specific to a given test case. You can specify these options in a file named mysql-test/t/test_name-master.opt. When a file named t/test_name-master.opt exists, mysql-test-run.pl examines it for extra options that the server needs to be run with when executing the test_name test case. If no server has yet been started or the current server is running with different options, mysql-test-run.pl restarts the server with the new options.

As a special case, the option --skip-core-file will be interpreted by mysql-test-run.pl, which will then block the server from producing any core files or crash dumps during this test. This may be useful for tests that intentionally crash the server.

Files in the mysql-test/t directory with names ending in -slave.opt are similar, but they are used for slave servers in replication tests.

Sometimes it's also necessary to execute some external commands before starting the server, such as creating a directory. If you add a file named t/test_name-master.sh, it will be executed by mysql-test-run.pl before it starts the server; a similar file may be created for the slave in replication tests.

Because the .sh file is executed through /bin/sh, it cannot be used on Windows, and any tests using such a file will automatically be skipped if you run on Windows. For this reason, this mechanism may be replaced with a more portable one in some future release of MySQL.