Calabash-cucumber ios：如何删除textField

Question

我正在尝试删除textField中的字符，使用--keyboard_enter_char＆＃34;删除＆＃34; - 这是我在步骤定义中的代码。

touch(query("textField")[0])        # touch the textField and bring up the keyboard, working
keyboard_enter_text("a")            # enter "a" into the textField, working
keyboard_enter_char "delete"        # I expect to see the "a" gone

所以执行keyboard_enter_char "delete"时

我收到了错误

typing character 'delete' is not yet supported when running with Instruments (RuntimeError) 

并且脚本停止。

有人能告诉我我做错了什么，或者我应该如何删除textField中的字符？谢谢！