为什么 Jest 不应该抛出错误? [英] Why does Jest throw an error when it should not?

问题描述

我有一个这样的功能:

const test = (match) => {
   if (match !== 'cat') {
     throw new TypeError()
   }
}

我的测试是:

describe('test', () => {
  it('must throw error'() => {
    try {
      test('cat')
    catch(err){
      expect(err).toStrictEqual(new TypeError())
    }
  }
}

但是测试通过了.它应该失败.为什么通过了?

But the test passed. It should fail. Why did it pass?

推荐答案

只有在未满足预期的情况下，测试才会失败.在您的情况下，因为没有抛出错误，所以甚至没有评估任何期望.因此测试通过.

Tests only fail if there is an unmet expectation. In your case, because no error is thrown, no expectation is ever even evaluated. Therefore the test passes.

要解决这个问题，要么:

To deal with this, either:

1. 确保使用 expect.assertions 评估一个期望:

describe('test', () => {
  it('must throw error'() => {
    expect.assertions(1);
    try {
      test('cat')
    catch(err){
      expect(err).toStrictEqual(new TypeError())
    }
  }
}

或

使用 .toThrow 处理错误 期望而不是自己抓住它:

handle the error with a .toThrow expectation rather than catching it yourself:

describe('test', () => {
  it('must throw error'() => {
    expect(() => test('cat')).toThrow(TypeError)
  }
}

请注意，作为 Estus Flask 指出，这只能在构造函数或错误消息上断言.

Note that, as Estus Flask pointed out, this can only assert on either the constructor or the message of the error.

这篇关于为什么 Jest 不应该抛出错误?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！