I followed the How-To document to start using Selenium in Mendix. It worked perfectly. But manually editing all the steps is tedious, time consuming and I'm way too lazy for that kind of task anyway. So I created a little plugin to help Selenium recognize Mendix page elements by their mx-name- classes. It also handles elements in grid rows. It can be found here. This reduces the work in Selenium IDE quite a bit! :-) Note that it only works with Mendix 5 because earlier releases do not generate the mx-name classes on the elements. Have fun!