stress is a tool that imposes CPU, memory, I/O, or disk stress on an operating system, so you can test if your applications work under high load, e.g. when almost out of memory.
How do I install Stress on CentOS?
Installing on Ubuntu is trivial:
sudo aptitude install stress. But I haven't found any package for CentOS, and what seems to be the homepage that "everyone" refers to returns 404 Not Found: http://weather.ou.edu/~apw/projects/stress/