# File test/test_params.rb, line 1595
    def test_argument_string
      init_arguments
      assert_equal('hi', @entry.args[0])
      @entry.set_arg_at(0, 'hello')
      assert_equal('hello', @entry.args[0])
      @entry.set_arg_at(0, nil) # allowed
      assert_exception(RuntimeError) {
        @entry.set_arg_at(0, :hi) # not allowed
      }
    end