While working on T161697 I have noticed that we did not upgrade WebdriverIO in a long time. We are currently using version 4.6.2. Our tests work fine up until version 4.7.1. Since version 4.8.0 our tests break because wdio tries to open http://127.0.0.1:8080/index.php... instead of http://127.0.0.1:8080/w/index.php... (please notice missing /w).
/w is configured in wdio.conf.js
Maybe this has caused the problem: make url act like url.resolve - closes #1946