如何用玩笑在代码中更深地模拟函数

Question

我试图模拟这个邮件功能，所以我每次测试我的代码时都不会发送邮件。但是嘲弄是行不通的。这段代码给了我错误：mockImplementation is not a function。

是调用 sendUserInvitationMail() 的 add 函数。邮件模块导出如下所示：

module.exports = {
  sendUserInvitationMail,
};

这是测试代码：

require('dotenv').config();
const { startWithCleanDb } = require('../../../utils/test.helpers');
const { add } = require('../invitation.service');
const { ADMIN_LEVELS, TABLES } = require('../../../constants');
const { AuthorizationError } = require('../../../errors');
const knex = require('../../../../db/connection');
const mailer = require('../../../mailer/index');

jest.mock('../../../mailer/index');

beforeEach(() => startWithCleanDb());


mailer.sendUserInvitationMail.mockImplementation(() => console.log('Mocked mail function called'));

mailer.sendUserInvitationMail();

describe('invitation.service', () => {
  describe('add', () => {
    it('adds an invitation to the db', async () => {
      expect.assertions(2);
      const result = await add(
        {
          email: 'tester@test.be',
          badgeNumber: '344d33843',
        },
        { currentZoneId: 1 },
        ADMIN_LEVELS.ADMINISTRATOR,
      );
      const invitation = (await knex.select('*').from(TABLES.INVITATIONS))[0];
      expect(invitation.id).toEqual(result.id);
      expect(invitation.email).toEqual(result.email);
    });

  });
});

Answer 1

在mailer中，sendUserInvitationMail是undefined，所以它没有mockImplementation的属性。

试试：

mailer.sendUserInvitationMail = jest.fn().mockImplementation(() => console.log('Mocked mail function called'));

或

mailer.sendUserInvitationMail = jest.fn(() => console.log('Mocked mail function called'));