Allow to force skip tests

This is useful for when a test depends on code not being loaded that
might be loaded by another test.

activesupport/test/core_ext/object/json_gem_encoding_test.rb

@@ -40,7 +40,7 @@ def to_json(*)
 
   private
     def require_or_skip(file)
-      require(file) || skip("'#{file}' was already loaded")
+      require(file) || force_skip("'#{file}' was already loaded")
     end
 
     def assert_same_with_or_without_active_support(subject)

tools/test_common.rb

@@ -14,5 +14,6 @@ def skip(message = nil, *)
           "This should never happen on CI."
       end
   end
+  ActiveSupport::TestCase.alias_method :skip, :force_skip
   ActiveSupport::TestCase.include(DisableSkipping)
 end