Contact's MessageEntityTest wrongly uses 'edit' access operation on entities instead of 'update'

Hmm... good question. So this is testing access control for contact messages, but contact messages don't implement any specific entity access (only for the create access). So this basically just tests the base access control logic that checks the admin permission - and the fact that the admin permission is set correctly on contact messages, which is why I think those tests were introduced at the time. So I think the tests are fine in terms of coverage. For context, this was introduced all the way back in #2427713: Contact module doesn't implement AccessControlHandler.

The thing is that the admin permission is checked regardless of the passed operation and we don't validate the operation in any other way either. So basically if you pass jump around (or whatever...) as the access operation it will grant access if you have the admin permission and it will deny access if you don't.

So I don't think there's anything missing in the test coverage and there's nothing functionally wrong. I think it does really make sense to change it, though, because update is the correct operation that is used all over core what (I presume) is meant to be tested in the test and, furthermore, edit is the correct operation for checking field access (i.e. $contactMessage->get('subject')->access('edit')) so this especially confusing and sets a bad example.

Random test failure (see #3267124: Temporarily skip failing tests) and then random checkout failure on the testbot. Back to RTBC now.

Another random failure: #3267754: AjaxTest is failing

...and #3055982: Remove resizing window in BlockFormMessagesTest::testValidationMessage