It is important for web hosts and administrators to test their web servers under stress conditions. Stress testing highlights any potential problem you may have with access to your websites. They simulate your web servers under heavy loads such as high numbers of user connections, downloads, requests and bandwidth.
The basic idea is that a load (heavy traffic) is placed on the server to produce stress to analyse future scalability problems. That is to say, if you have two web servers running and you expect a high demand in the months of July and August, stress testing your servers might highlight problems for the future, which in turn will highlight whether you need to purchase and set up another web server.
There are a lot of software tools available on the Internet for testing servers. Visit, for example: