为什么Jest会在不应出现的时候抛出错误? [英] Why does Jest throw an error when it should not?

问题描述

我有这样的功能:

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.为什么会通过?

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

推荐答案

只有在未满足期望的情况下，测试才会失败.在您的情况下，因为不会引发任何错误，所以甚至不会评估任何期望.因此，测试通过了.

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.

要解决此问题，请执行以下任一操作:

To deal with this, either:

1. 确保使用 expect.assertions :

1. make sure exactly one expectation is evaluated using expect.assertions:

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

或

使用 .toThrow 期望来处理错误而不是自己捉住它:

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，如 Estus Flask

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会在不应出现的时候抛出错误?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！