Rails test suite hangs when using multiple webdrivers (Cuprite + headless Selenium)

[Kyle Shipley]

I am working on a project using Cuprite as our main webdriver. We added a shadow DOM element to one page recently. It seems like Cuprite's support for shadow DOM is somewhat limited, so we decided to add Selenium as a driver and limit it to just this one page.

When using both drivers, we are experiencing an issue where running `rails test:all` hangs and never returns. In some cases, I cannot even Ctrl+C the process - I have to find the PID and kill it.

I created a couple small repositories this morning to attempt to reproduce this issue as minimally as possible:

https://github.com/shipstar/system-tests-with-multiple-webdrivers - this reflects the current setup in our project, which is Rails 7 + system tests

https://github.com/shipstar/rspec-with-multiple-webdrivers - just to see if this issue was limited to Rails system tests, I also made this small repo which uses RSpec instead and saw the same issue

I'm not sure where to go next on debugging this one, but happy to help if anyone has ideas.

Thanks!

- Kyle