# File test/unit/assertions.rb, line 88
      def assert_instance_of(klass, object, message="")
        _wrap_assertion do
          assert_equal(Class, klass.class, "assert_instance_of takes a Class as its first argument")
          full_message = build_message(message, object, klass, object.class) do |arg1, arg2, arg3|
            "<#{arg1}> expected to be an instance of\n" + 
            "<#{arg2}> but was\n" +
            "<#{arg3}>"
          end
          assert_block(full_message) { klass == object.class }
        end
      end