Tests: More complete mock to prevent php 8.1 warning
Tests: More complete mock to prevent php 8.1 warning

fixes:
ContainmentSetTest::testCachedListInnerListIsOnlyCalledOnce
strtr(): Passing null to parameter #1 ($string) of type string is deprecated

Change-Id: I9bb916383eda1176a2d56c06770a60c28431dfda

wikimedia/mediawiki-extensions-Echo,wikimedia/mediawiki-extensions-Echo,wikimedia/mediawiki-extensions-Echo,wikimedia/mediawiki-extensions-Echo