期望承诺解决或拒绝没有适当地失败测试与摩卡和chai-as-promise

Question

使用Mocha和chai-as-promised，我试图测试我的承诺正在被解决并被正确拒绝。但是chai-as-promise所给出的expect函数并没有正确地导致测试失败。例：

test.js

const chai = require('chai')
chai.use(require('chai-as-promised'))
const expect = chai.expect

describe('foo', () => {
  it('resolve expected', () => {
    expect(new Promise((res,rej) => {res()})).to.be.fulfilled
  })
  it('resolve unexpected', () => {
    expect(new Promise((res,rej) => {res()})).to.be.rejected
  })
  it('reject expected', () => {
    expect(new Promise((res,rej) => {rej()})).to.be.rejected
  })
  it('reject unexpected', () => {
    expect(new Promise((res,rej) => {rej()})).to.be.fulfilled
  })
})

当我执行mocha test.js时：

  foo
    ✓ resolve expected
    ✓ resolve unexpected
(node:2659) UnhandledPromiseRejectionWarning: Unhandled promise rejection (rejection id: 1): AssertionError: expected promise to be rejected but it was fulfilled with undefined
(node:2659) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.
    ✓ reject expected
    ✓ reject unexpected
(node:2659) UnhandledPromiseRejectionWarning: Unhandled promise rejection (rejection id: 4): AssertionError: expected promise to be fulfilled but it was rejected with undefined


  4 passing (10ms)

您可以看到断言错误似乎被抛出，但摩卡不会接受它们。如何让摩卡识别失败？

Answer 1

正如我们确认的那样，并且为了将来参考，问题是您没有在每个测试中返回断言。

it('reject expected', () => {
  return expect(new Promise((res,rej) => {rej()})).to.be.rejected
})
it('reject unexpected', () => {
  return expect(new Promise((res,rej) => {rej()})).to.be.fulfilled
})

这就是为什么测试通过但后来在最终返回时打印出“未处理”的承诺。 return关键字通知mocha等待异步函数解析/拒绝。

Answer 2

或者使用chai-as-promise库，您可以尝试使用chai.should并调用.notify来表示其“已完成”。像这样：

const chai = require('chai');
chai.use(require('chai-as-promised'));
chai.should();

const expect = chai.expect;

describe('foo', () => {
    it('resolve expected', () => {
        expect(new Promise((res, rej) => { res(); })).to.be.fulfilled;
    });
    it('resolve unexpected', (done) => {
        // expect(new Promise((res, rej) => { res(); })).to.be.rejected;
        new Promise((res, rej) => { res(); }).should.be.rejected.and.notify(done);
    });
    it('reject expected', (done) => {
        // expect(new Promise((res, rej) => { rej(); })).to.be.rejected;
        new Promise((res, rej) => { rej(); }).should.be.rejected.and.notify(done);
    });
    it('reject unexpected', (done) => {
        // expect(new Promise((res, rej) => { rej(); })).to.be.fulfilled;
        new Promise((res, rej) => { rej(); }).should.be.fulfilled.and.notify(done);
    });
});

这样mocha将识别测试失败：

foo
    √ resolve expected
    1) resolve unexpected
    √ reject expected
    2) reject unexpected


  2 passing (37ms)   2 failing

  1) foo
       resolve unexpected:
     AssertionError: expected promise to be rejected but it was fulfilled with undefined


  2) foo
       reject unexpected:
     AssertionError: expected promise to be fulfilled but it was rejected with undefined

检查chai-as-promised doc进一步参考here