MySQL Benchmark Suite is a toolkit for basic load testing (http://dev.mysql.com/doc/refman/5.5/en/mysql-benchmarks.html). If you install MySQL from source, or download the mysql-bench package, you can use several very basic testing scripts. These have limited features, including being limited to a single execution thread, and should only be considered if there are no other means of load testing available. Consult the MySQL documentation for more information.
MySQLslap (http://dev.mysql.com/doc/refman/5.5/en/mysqlslap.html) is commonly used, but simple script is included as a client application with the GA distribution of MySQL. It is typically used to generate load or function as a simulation mechanism in a larger scale custom load testing system where it is wrapped via a parent script or application to control data visualization and iteration controls. It has the following options:
Iteration pre-test command execution + sql query
Iteration post-test command execution...