量角器 ElementArrayFinder .last() [object Object] 没有方法 'indexof'

protractor ElementArrayFinder .last() [object Object] has no method 'indexof'

我正在尝试 运行 完成教程 http://angular.github.io/protractor/#/tutorial

当我尝试使用 .first().last() 方法获取元素时 测试失败并出现错误:

TypeError Object [object Object] has no method 'indexof'

这里是spec.js

var firstNumber = element(by.model('first'));
var secondNumber = element(by.model('second'));
var go = element(by.id('gobutton'));
var latest = element(by.binding('latest'));
var history = element.all(by.repeater('result in memory'));

beforeEach(function() {
    browser.get('http://juliemr.github.io/protractor-demo/');
});
//...other tests passed

it('should have a history', function(){
    firstNumber.sendKeys(1);
    secondNumber.sendKeys(2);
    go.click();

    expect(history.count()).toEqual(1);
    // expect(history.last()).toContain('1 + 2'); //error here

    firstNumber.sendKeys(3);
    secondNumber.sendKeys(5);
    go.click();

    expect(history.count()).toEqual(2);
    // expect(history.first()).toContain('3 + 5'); //and here
});

关于这个 ElementArrayFinder API 应该 运行 没问题

我正在使用

您可能是想期待元素的文本

expect(history.last().getText()).toContain('1 + 2');
expect(history.first().getText()).toContain('3 + 5');