Don’t miss this important note if your planning to run tests against Internet Explorer using Selenium Grid
I tried to run tests in parallel against IE using the selenium grid for a few days before I found this important message on the selenium grid FAQ.
If you try to run multiple selenium remote controls for IE on one machine it will work for a while. Your test will execute without any problems, but then you start getting sporadic error messages from IE. I assumed that the xpath expressions I was using for the tests in Firefox were throwing errors in IE. I tried different configurations for security settings in IE for a while and then I finally found out that it was a memory sharing issue that prevents the selenium remote from launching more than one IE instance. For now I am just requesting more VMs to run a single IE remote on each. I use ruby with deep test to run test in parallel on the grid. I configure deep test to run 6 tests at a time, so I would only need 6 VMs for IE to run.
It puzzling to me that Watin tests run in parallel against IE without any problems on the same machine, but selenium tests cannot. For now I will add more VMs and wait for Selenium Grid 1.2 to fix the IE problem.