Hi,
I have made a few more changes and now test cases are getting passed.
$ npm run selenium-test
selenium-test wdio tests/selenium/wdio.conf.js
Execution of 2 spec files started at 2021-10-27T11:43:14.577Z
[0-0] RUNNING in chrome - /tests/selenium/specs/page_previews.js [0-0] PASSED in chrome - /tests/selenium/specs/page_previews.js [0-1] RUNNING in chrome - /tests/selenium/specs/reference_previews.js [0-1] PASSED in chrome - /tests/selenium/specs/reference_previews.js
"dot" Reporter: .......
Spec Files: 2 passed, 2 total (100% completed) in 00:00:18.
Thanks for your help. I have also updated the docs https://www.mediawiki.org/w/index.php?title=MediaWiki-Docker/Extension/Popup....
Cheers, Agha Saad