typescript - 用 Jest 在 typescript 中模拟导入的类

Question

我正在尝试使用 jest 来模拟 typescript 类中的导入类，以下代码用于主程序(我从函数内部删除了一些代码，但它仍然应该清楚我正在尝试做什么)

import * as SocketIO from "socket.io";

import {AuthenticatedDao} from "../../dao/authenticated.dao";

export default class AuthenticationService {
    private readonly _authenticatedDao: AuthenticatedDao = AuthenticatedDao.Instance;
    private readonly _io;

    constructor(socketIo: SocketIO.Server) {
        this._io = socketIo;
    }

    public authenticateUser(username: string, password: string, clientSocketId: string): void {
        this._authenticatedDao.authenticateUser(username, password).then((authenticatedUser) => {

        }).catch(rejected => {

        });
    }
}


import {createServer, Server} from 'http';
import * as express from 'express';
import * as socketIo from 'socket.io';
import {LogincredentialsDto} from "./models/dto/logincredentials.dto";
import {config} from './config/config';
import AuthenticationService from "./services/implementation/authentication.service";
import {Logger} from "./helperclasses/logger";
import {format} from "util";

export class ClassA {
    private readonly _configPort = config.socketServerPort;

    private readonly _logger: Logger = Logger.Instance;
    private _app: express.Application;
    private _server: Server;
    private _io: socketIo.Server;
    private _socketServerPort: string | number;
    private _authenticationService: AuthenticationService;


    constructor() {
        this.configure();
        this.socketListener();
    }

    private configure(): void {
        this._app = express();

        //this._server = createServer(config.sslCredentials, this._app);
        this._server = createServer(this._app);

        this._socketServerPort = process.env.PORT || this._configPort;
        this._io = socketIo(this._server);

        this._server.listen(this._socketServerPort, () => {
            this._logger.log(format('Server is running on port: %s', this._socketServerPort));
        });

        this._authenticationService = new AuthenticationService(this._io);
    }


    private socketListener(): void {
        this._io.on('connection', (client) => {
                client.on('authenticate', (loginCreds: LogincredentialsDto) => {
                    console.log(loginCreds.username, loginCreds.password, client.id);
                    this._authenticationService.authenticateUser(loginCreds.username, loginCreds.password, client.id);
                });
            }
        );
    }
}

我正在尝试模拟“AuthenticationService”中的函数“authenticateUser”，而不是调用我想模拟 promise 的普通代码。我尝试使用 https://jestjs.io/docs/en/es6-class-mocks 中提供的示例但是当我尝试执行以下操作时:

import AuthenticationService from '../src/services/implementation/authentication.service';
jest.mock('./services/implementation/authentication.service');

beforeEach(() => {
    AuthenticationService.mockClear();
});

it('test', () => {

    // mock.instances is available with automatic mocks:
    const authServerInstance = AuthenticationService.mock.instances[0];

我得到这个错误: 错误:(62, 31) TS2339:类型“typeof AuthenticationService”上不存在属性“mock”。

我在这里做错了什么？我是否应该以不同的方式模拟类/函数，因为它使用的是 promise ？

Answer 1

问题

AuthenticationService 的类型不包括 mock 属性，因此 TypeScript 会抛出错误。

---

详情

jest.mock 创建一个 automatic mock该模块“用模拟构造函数替换 ES6 类，并用始终返回 undefined 的模拟函数替换其所有方法”。

在这种情况下，authentication.service.ts 的default 导出是一个 ES6 类，因此它被替换为模拟构造函数。

mock 构造函数有一个 mock 属性，但 TypeScript 不知道它并且仍然将 AuthenticationService 视为原始类型。

---

解决方案

使用 jest.Mocked 让 TypeScript 知道 jest.mock 引起的类型变化:

import * as original from './services/implementation/authentication.service';  // import module
jest.mock('./services/implementation/authentication.service');

const mocked = original as jest.Mocked<typeof original>;  // Let TypeScript know mocked is an auto-mock of the module
const AuthenticationService = mocked.default;  // AuthenticationService has correct TypeScript typing

beforeEach(() => {
  AuthenticationService.mockClear();
});

it('test', () => {

    // mock.instances is available with automatic mocks:
    const authServerInstance = AuthenticationService.mock.instances[0];