This MediaWiki extension shows a slider allowing selecting and comparing of revisions on a diff page
Check out this extension into the extensions folder of your MediaWiki installation and add the following line to your LocalSettings.php:
wfLoadExtension( 'RevisionSlider' );
Before executing tests run the following in the root directory of the extension once:
composer install
npm install
For the tests run:
composer test
node_modules/.bin/grunt test
See https://www.mediawiki.org/wiki/Manual:JavaScript_unit_testing#Run_the_tests
See tests/selenium/README.md