为什么我的自定义命令无法与nightwatch-api框架一起使用

Question

我正在尝试将较旧的Nightwatch-Cucumber框架迁移到Nightwatch-api。一切都与WaitForText自定义命令分开。但是，它适用于旧实例。

这是尝试运行自定义命令时出现的错误：

Error while running "WaitForText" command: Cannot read property 'isES6Async' of undefined
TypeError: Error while running "WaitForText" command: Cannot read property 'isES6Async' of undefined
    at queuedCommandFn (/home/kieran/Documents/automation/updated-framework/node_modules/nightwatch/lib/api/_loaders/command.js:195:35)
    at CommandInstance.WaitForText.check (/home/kieran/Documents/automation/updated-framework/lib/CustomCom/WaitForText.js:34:5)
    at CommandInstance.WaitForText.command (/home/kieran/Documents/automation/updated-framework/lib/CustomCom/WaitForText.js:20:10)
    at /home/kieran/Documents/automation/updated-framework/node_modules/nightwatch/lib/api/_loaders/command.js:154:29
    at processTicksAndRejections (internal/process/task_queues.js:93:5)

这是WaitForText.js定制命令：

var util = require('util');
var events = require('events');

function WaitForText() {
    events.EventEmitter.call(this);
    this.startTime = null;
}

util.inherits(WaitForText, events.EventEmitter);

WaitForText.prototype.command = function (element, getter, checker, ms) {
    this.startTime = new Date().getTime();
    var self = this;
    var message;

    if (typeof ms !== 'number') {
        ms = 1000;
    }

    this.check(element, getter, checker, function (result, loadedMs) {
        if (result) {
            message = 'Expression was true after ' + (loadedMs - self.startTime) + ' ms.';
        } else {
            message = 'Expression wasn\'t true in ' + ms + ' ms.';
        }
        self.client.assertion(result, 'expression false', 'expression true', message, true);
        self.emit('complete');
    }, ms);
    return this;
};

WaitForText.prototype.check = function (element, getter, checker, cb, maxTime) {
    var self = this;
    getter(element, function (result) {
        var now = new Date().getTime();
        if (result.status === 0 && checker(result.value)) {
            cb(true, now);
        } else if (now - self.startTime < maxTime) {
            setTimeout(function () {
                self.check(element, getter, checker, cb, maxTime);
            }, 1000);
        } else {
            cb(false);
        }
    });
};

module.exports = WaitForText;

我不知道从哪里开始，因为我不了解自定义命令的工作原理，它已经包含在以前的框架中。

任何帮助将不胜感激。