If a test case needs a specific client option, you can specify such options in a file named testname-client.opt.

When a test case has its own -client.opt file, mysql-test-run.pl examines it for any additional options that the mysqltest should run with while executing the test case.

For example, consider a test case example.test needs latin1 as default character set for client and connection, then that option can be specified in example-client.opt file.

--default-character-set=latin1

You may refer to environment variables in the option file, using the usual $VAR_NAME syntax. It is also possible to refer to optional variables using the syntax $?VAR_NAME. This will be replaced with an empty string if the variable is not set.