Add automated test for "Change date format"

The manual test is here: https://test.xwiki.org/xwiki/bin/view/Administration%20Tests/Change%20Date%20Format

The test verifies that changing the Date Format from Administration works properly.

Matrix discussion: https://matrix.to/#/!ikPtGZaGWtyblizzlR:matrix.xwiki.com/$1645697560500AjRrt:matrix.xwiki.com?via=matrix.org&via=matrix.xwiki.com&via=caubin.fr

Ilie Andriuta: Hi! Continuing the manual tests migration, there is a test about checking if changing the Date Format from Administration is working properly: https://test.xwiki.org/xwiki/bin/view/Administration%20Tests/Change%20Date%20Format
I've checked https://github.com/xwiki/xwiki-platform/blob/73b07f8352d1716b9945b577d6e4a3334f058a77/xwiki-platform-core/xwiki-platform-administration/xwiki-platform-administration-test/xwiki-platform-administration-test-pageobjects/src/main/java/org/xwiki/administration/test/po/LocalizationAdministrationSectionPage.java but couldn't find automated tests for it.
Can you please confirm whether the automated test exists for it or not and maybe providing the link to it?

Thanks!
Vincent Massol: checking
Vincent Massol: hmm clover used to show the tests contributing coverage to a method but I don't see it at http://maven.xwiki.org/site/clover/20201213/clover-commons+rendering+platform-20201213-0735/com/xpn/xwiki/XWiki.html?line=6467#src-6467
(in any case it wouldn't help much since almost all tests exercise this method )
Ilie Andriuta: so I don't see any test verifying https://github.com/xwiki/xwiki-platform/blob/2c483c33e73b05763515eaf19d7bf8fbdda3bfe3/xwiki-platform-core/xwiki-platform-flamingo/xwiki-platform-flamingo-skin/xwiki-platform-flamingo-skin-resources/src/main/resources/flamingo/contentheader.vm#L43
should be easy to add a PageTest for it
Ilie Andriuta: ok, thanks, I'll create a task for it
Vincent Massol: I also don't see any test testing XWiki.formatDate() which is less nice
and we need to move this method out of the XWiki class...