Question

我试图用Jest CLI测试一个承诺，这个代码在它在浏览器中运行时应该执行。但是我想开始为它编写测试。

class ListCollection {
  constructor() { 
    this.items = new Array();
  }

  addItem(string) {
    const addItemPromise = new Promise(
      function (resolve, reject) {
        // set up async getting like a XMLHttpRequest
        setTimeout( () => {
          this.items.push(string);
          resolve(string);
        }.bind(this), 2000);
      }.bind(this)
    );
    return addItemPromise;
  }
}

目前，我正试图让这个非常基本的测试工作。我根据documentation which links to jasmine-pit使用pit进行测试。

jest.dontMock('../collections');

import Collection       from '../collections';

describe("Collection", () => {
    let collection;

    beforeEach(() => {
        collection = new Collection();
    });

    describe("Adding an item", () => {
        pit('Spec 1', function () {
            return collection.addItem("Hello World").then(function (string) {
                expect(string).toBe("Hello World");
            });
        });
    });
})

当我使用babel-node ./node_modules/.bin/jest运行我的测试时，上面的测试因为它的堆栈跟踪而失败。值得注意的是，我得到Promise is not defined。

Rollos-Mac-Pro:react-boilerplate Rollo$ babel-node ./node_modules/.bin/jest
Using Jest CLI v0.4.0
 FAIL  app/collections/__tests__/collectionTests.js
ReferenceError: /Users/Rollo/react-boilerplate/app/collections/__tests__/collectionTests.js: /Users/Rollo/react-boilerplate/app/collections/collections.js: **Promise is not defined**
    at ListCollection.addItem (/Users/Rollo/react-boilerplate/app/collections/collections.js:24:34)
    at /Users/Rollo/react-boilerplate/app/collections/collections.js:48:12
    at Object.runContentWithLocalBindings (/Users/Rollo/react-boilerplate/node_modules/jest-cli/src/lib/utils.js:361:17)
    at Loader._execModule (/Users/Rollo/react-boilerplate/node_modules/jest-cli/src/HasteModuleLoader/HasteModuleLoader.js:250:9)
    at Loader.requireModule (/Users/Rollo/react-boilerplate/node_modules/jest-cli/src/HasteModuleLoader/HasteModuleLoader.js:916:12)
    at Loader.requireModuleOrMock (/Users/Rollo/react-boilerplate/node_modules/jest-cli/src/HasteModuleLoader/HasteModuleLoader.js:937:17)
    at /Users/Rollo/react-boilerplate/app/collections/__tests__/collectionTests.js:7:34
    at Object.runContentWithLocalBindings (/Users/Rollo/react-boilerplate/node_modules/jest-cli/src/lib/utils.js:361:17)
    at Loader._execModule (/Users/Rollo/react-boilerplate/node_modules/jest-cli/src/HasteModuleLoader/HasteModuleLoader.js:250:9)
    at Loader.requireModule (/Users/Rollo/react-boilerplate/node_modules/jest-cli/src/HasteModuleLoader/HasteModuleLoader.js:916:12)
    at jasmineTestRunner (/Users/Rollo/react-boilerplate/node_modules/jest-cli/src/jasmineTestRunner/jasmineTestRunner.js:242:16)
    at /Users/Rollo/react-boilerplate/node_modules/jest-cli/src/TestRunner.js:371:12
    at _fulfilled (/Users/Rollo/react-boilerplate/node_modules/jest-cli/node_modules/q/q.js:798:54)
    at self.promiseDispatch.done (/Users/Rollo/react-boilerplate/node_modules/jest-cli/node_modules/q/q.js:827:30)
    at Promise.promise.promiseDispatch (/Users/Rollo/react-boilerplate/node_modules/jest-cli/node_modules/q/q.js:760:13)
    at /Users/Rollo/react-boilerplate/node_modules/jest-cli/node_modules/q/q.js:574:44
    at flush (/Users/Rollo/react-boilerplate/node_modules/jest-cli/node_modules/q/q.js:108:17)
    at /Users/Rollo/react-boilerplate/node_modules/jest-cli/src/lib/FakeTimers.js:325:7
    at process._tickCallback (node.js:448:13)

我不知道如何解决这个问题。我使用的节点版本必须是0.10.x，否则我无法运行Jest-CLI。但节点版本0.10.x并没有承诺。我也不了解Jest-CLI如何使用我的ES6类和语法，但却没有认识到Promises。

知道如何在我的设置中获得承诺吗？

修改

我已将es6-promise polyfill添加到我的测试文件的顶部，并标记它不会被模拟。这提供了足够的解决方案。

jest.dontMock('es6-promise');
require('es6-promise').polyfill();

Answer 1

输出提到babel-node，这意味着babel作为需求挂钩运行，动态地将ES6编译为ES5。您需要为本机承诺包含一个垫片，并将其公开为global.Promise。我推荐这个：https://github.com/jakearchibald/es6-promise

Answer 2

用babel-jest替换jest scriptPreprocessor应该适用于所有es6可比性问题

https://babeljs.io/docs/using-babel/#jest

使用Jest CLI时如何让Promise工作？

2 个答案: