# File lib/test/unit/assertions.rb, line 746
      def assert_fail_assertion(message=nil)
        _wrap_assertion do
          full_message = build_message(message,
                                       "Failed assertion was expected.")
          assert_block(full_message) do
            begin
              yield
              false
            rescue AssertionFailedError
              true
            end
          end
        end
      end