Few toos in my mind which can be used for stress testing of your mysql server.
hammerdb: one of the open source database (i.e. mysql, oracle, sql server, etc) load testing tool.
mysql-stress-test-pl: Helps to run a test case in mysql server and also offer to compare the results of the test run. Following link provides all about syntax and their usages to run test cases: https://dev.mysql.com/doc/mysqltest/2.0/en/mysql-stress-test-pl.html
mysqltuner: performance tunning scripts helps to check current status of the server provides helpful recommendation as well. Please refer following link for the script: https://raw.githubusercontent.com/major/MySQLTuner-perl/master/mysqltuner.pl
In addition, I have not used sysbench, mysqlslap but heard good feedback about them. You can try if you have time to explore.