Now https://gerrit.wikimedia.org/r/#/c/302944/ is merged, phpunit tests can be autodiscovered by moving them into the correct place. See https://gerrit.wikimedia.org/r/#/c/302958/ for example
Once this has been done, UnitTestsList subscribers can be removed
Ready to go list:
[x] AbuseFilter
[x] ActiveAbstract
[x] AntiSpoof
[x] ArticlePlaceholder
[x] Babel
[ ] BaseHooks
[x] BetaFeatures
[ ] BounceHandler
[c] Capiunto
[x] CentralAuth
[x] Cognate
[x] CollaborationKit
[x] CommonsMetadata
[x] ConfirmEdit
[ ] DonationInterface
[x] Elastica
[x] EventBus
[x] ExtensionDistributor
[x] Gadgets
[x] GlobalCssJs
[x] GoogleAPIClient
[x] GuidedTour
[x] Kartographer
[x] LocalisationUpdate
[x] LoginNotify
[ ] MaintenanceShell
[x] MassMessage
[x] Math
[ ] MathSearch
[x] MobileFrontend
[ ] MolHandler
[ ] Newsletter
[ ] OAuthAuthentication
[x] ORES
[x] PageAssessments
[ ] PageForms
[x] ParserFunctions
[ ] PhpTags
[ ] PhpTagsFunctions
[ ] PhpTagsWidgets
[ ] PhpTagsWiki
[x] ProofreadPage
[ ] QuickSearchLookup
[ ] SendGrid
[ ] Sentry
[x] TemplateData
[x] TemplateStyles
[x] TextExtracts
[x] Thanks
[x] TitleBlacklist
[x] TwnMainPage
[x] UploadWizard
[x] UrlShortener
[x] UserMerge
[x] WikibaseMediaInfo
[x] WikibaseQuality
[ ] Wikidata
[x] WikidataPageBanner
[x] WikimediaEvents
[x] WikimediaIncubator