Ensure all code is tested

[JeroenDeDauw]

Get https://app.codecov.io/gh/ProfessionalWiki/EDTF to 100%

Add missing @covers and missing tests.

Most missing coverage on codecov is likely due to due missing @covers tags. Keep in mind we want all logic to be tested. This requirement is more strict than line code coverage.

[mzeinstra]

Friendly warning that since you've exposed en.json to Translatewiki some of your test could fail due to changes in the community. Right @JeroenDeDauw

[JeroenDeDauw]

Indeed