期望承诺解决或拒绝并不能正确地通过 mocha 和 chai-as-promised 的测试

Question

使用Mocha和chai-as-promised，我试图测试我的承诺是否得到正确解决和拒绝。但是expect由 chai-as-promised 提供的功能并没有正确地导致测试失败。例子：

测试.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：

  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 mocha 没有发现它们。我怎样才能让摩卡识别失败？

Answer 1

正如我们所确认的，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了，但后来在它最终返回时打印了一个“未处理”的承诺。该return/拒绝关键字运筹学与摩卡等待异步功能来解决。