# File lib/test/unit/exceptionhandler.rb, line 10
        def included(base)
          base.extend(ClassMethods)

          observer = Proc.new do |test_case, _, _, value, method_name|
            if value
              @@exception_handlers.unshift(method_name)
            else
              @@exception_handlers -= [method_name]
            end
          end
          base.register_attribute_observer(:exception_handler, &observer)
        end