Right now, the RevisionSlider Selenium tests are written in Ruby. However, it was decided to use node.js for selenium tests.
This still needs to be done for the RevisionSlider.
See T180246: Port ElectronPdfService Selenium tests from Ruby to Node.js for an example where the tests were already ported
🏝 443113 (mediawiki/extensions/RevisionSlider): WIP The first sample Selenium test in Node.js