Software testing in general is a very difficult task and testing web-based applications can be even harder due to the market pressure and short time response to a larger scale of users. We present a case study that demonstrates how to test a complex web-based application system by using a low-cost open-source testing tool in order to conduct performance testing and load testing. The open-source testing tool we chose greatly helped us evaluate the different performance levels of a complex Transportation Management System (TMS) and identify two critical performance issues before the actual deployment. This tool turned out to be very cost-effective and useful to identify the potential performance problems before actual production or implementation.