Stress/load testing unit tests?

I have some tests for a booking system project - which tests that a customer can book a space on a particular event. This works well when run sequentially.

However, I want to simulate 10's/100's of people all trying to book the same event and space at the same time. Is there any way to run load test tests in the same way that you can load tests urls with ab or siege?

Or is it just a case that I make simple 'test' pages and hit them lots of times.