Typescript Error: Argument of type 'number' is not assignable to parameter of type 'Expected<Promise<number>>'

Question

我有以下函数执行失败：

it('should show three items', () => {
    const EXPECTED_NUMBER_OF_ITEMS: number = 3;
    const countOfTabElements: Promise<number> = page.listOfTabs.count();
    expect(countOfTabElements).toBe(EXPECTED_NUMBER_OF_ITEMS);
});

当我执行它时抛出以下错误：

Argument of type 'number' is not assignable to parameter of type 'Expected>'. (2345)

知道为什么吗？

Answer 1

尝试：

it('should show three items', () => {
    const EXPECTED_NUMBER_OF_ITEMS: number = 3;
    page.listOfTabs.count().then(value => {
        expect(value).toBe(EXPECTED_NUMBER_OF_ITEMS);
    });
});

Answer 2

作为@Nitzan Tomer 的替代答案，您应该可以使用async/await（TS >= 2.1 用于定位 ES5）

it('should show three items', async () => {
    const EXPECTED_NUMBER_OF_ITEMS: number = 3;
    const value = await page.listOfTabs.count();
    expect(value).toBe(EXPECTED_NUMBER_OF_ITEMS);
});

（作为旁注，我相信您需要相当新版本的 Mocha 才能正确处理承诺拒绝）

Answer 3

我会说使用 async 和 await 以最少的代码更改来处理 promise 对象。

// no changes to page.po.ts. handle async and await in .spec.ts file
import {browser, by, element} from 'protractor';

export class HomePage {

  navigateTo() {
    return browser.get('/');
  }

  getParagraphText() {
    return element(by.css('cfs-root h1')).getText();
  }

}

//page.e2e-spec.ts
import {HomePage} from './home.po';

describe('ng-app App', () => {
  let page: HomePage;

  beforeEach(() => {
    page = new HomePage();
  });

  it('should display the page heading.', async () => {   // notice the callback is a async function
    page.navigateTo();
    expect(await page.getParagraphText()).toBe('cfs works!');  //here we are using await to handle the promise
    page.getHomeSearchHeading().then((text) => {
      expect(text).toEqual('Universal Data Catalog');
    });
  });

});

Typescript Error: Argument of type 'number' is not assignable to parameter of type 'Expected<Promise<number>>'

Typescript Error: Argument of type 'number' is not assignable to parameter of type 'Expected<Promise<number>>'

javascript

typescript

e2e-testing