I also attempted to fix other styleguide violations such as
{ a: :b } over {a: :b} and foo(b: 'bar') over foo( b: 'bar' ).

removed use of AR in AMo tests and removed testing of scopes (:on) in individual validation tests and moved them to their own test file

No need to use ValidationsRepairHelper hack on ActiveModel anymore, Model.reset_callbacks(:validate) is enough. However, tests in ActiveRecord are still coupled, so moved ValidationsRepairHelper back there.