如何正确地使模拟在Jest中抛出错误？

Question

我正在使用Jest测试我的GraphQL api.

我正在为每个查询/突变使用单独的测试套装

我有2次测试(每一个在一个单独的测试套),其中我嘲笑一个函数(即,流星的callMethod),其在突变使用.

  it('should throw error if email not found', async () => {
    callMethod
      .mockReturnValue(new Error('User not found [403]'))
      .mockName('callMethod');

    const query = FORGOT_PASSWORD_MUTATION;
    const params = { email: 'user@example.com' };

    const result = await simulateQuery({ query, params });

    console.log(result);

    // test logic
    expect(callMethod).toBeCalledWith({}, 'forgotPassword', {
      email: 'user@example.com',
    });

    // test resolvers
  });

当console.log(result)我得到

{ data: { forgotPassword: true } }

这种行为不是我想要的,因为在.mockReturnValue我抛出一个错误,因此期望result有一个错误对象

然而,在此测试之前,另一个是运行

 it('should throw an error if wrong credentials were provided', async () => {
    callMethod
      .mockReturnValue(new Error('cannot login'))
      .mockName('callMethod');

它工作正常,错误抛出

我想问题是测试完成后mock不会被重置.在我的jest.conf.js我 clearMocks: true

每个测试套装都在一个单独的文件中,我在测试之前模拟函数:

import simulateQuery from '../../../helpers/simulate-query';

import callMethod from '../../../../imports/api/users/functions/auth/helpers/call-accounts-method';

import LOGIN_WITH_PASSWORD_MUTATION from './mutations/login-with-password';

jest.mock(
  '../../../../imports/api/users/functions/auth/helpers/call-accounts-method'
);

describe('loginWithPassword mutation', function() {
...

UPDATE

当我.mockReturnValue用.mockImplementation预期的一切代替时:

callMethod.mockImplementation(() => {
  throw new Error('User not found');
});

但这并不能解释为什么在另一个测试中.mockReturnValue工作得很好......

Answer 1

改变.mockReturnValue带.mockImplementation:

yourMockInstance.mockImplementation(() => {
  throw new Error();
});

Answer 2

对于承诺，可以使用https://jestjs.io/docs/mock-function-api#mockfnmockrejectedvaluevalue

test('async test', async () => {
  const asyncMock = jest.fn().mockRejectedValue(new Error('Async error'));

  await asyncMock(); // throws "Async error"
});

要测试是否引发错误，可以使用https://eloquentcode.com/expect-a-function-to- throw-an-exception-in-jest

const func = () => {
  throw new Error('my error')
}
it('should throw an error', () => {
    expect(func).toThrow()
})

Answer 3

对于 Angular + Jest：

import { throwError } from 'rxjs';

yourMockInstance.mockImplementation(() => {
  return throwError(new Error('my error message'));
});