As the size of programs grows, it becomes more difficult to understand the code. Therefore, when changing the code, random embedding of errors is also more likely. Ideally, it is advisable to test all existing features every time we change the source code, but it is not easy to test all existing features frequently because testing is time-consuming and costly. Therefore, it is necessary to consider automated testing. There are many benefits to automating testing. Most are related to the repeatability of the tests and the speed at which they can be performed. There are a number of commercial and open source tools that can help develop testing automation. One is Selenium.