如何使用Jest正确地模拟重载的类型记录函数

Question

我试图在一个实例上使用类型记录和Jest来模拟一个函数。然后是谷歌Auth的一个OAuth2Client。下面是我正在测试的模块：

sample.ts

import {OAuth2Client } from "google-auth-library";

export async function accessToken(): Promise<string | undefined> {
    const client: OAuth2Client = new OAuth2Client(
        "clientId", "clientSecret", "https://redirect.com"
    );
    const response = await client.getToken("code");
    return response?.tokens.access_token;
}

对于测试，我想从getToken调用返回一个固定的响应。使这变得更加复杂的是，getToken是重载的，而google-auth-library是类型记录。

getToken(code: string): Promise<GetTokenResponse>;
getToken(options: GetTokenOptions): Promise<GetTokenResponse>;
getToken(code: string, callback: GetTokenCallback): void;
getToken(options: GetTokenOptions, callback: GetTokenCallback): void;

这是我的考验：

sample.test.ts

import { OAuth2Client } from 'google-auth-library';
import {accessToken} from "./sample";
import {GetTokenResponse} from "google-auth-library/build/src/auth/oauth2client";

type GetTokenByCode = (code: string) => Promise<GetTokenResponse>

const oAuth2Client = jest.spyOn(OAuth2Client.prototype, 'getToken') as unknown as jest.MockedFunction<GetTokenByCode>;
oAuth2Client.mockImplementation((code: string) => {
    if (code != "code") return Promise.reject("Unexpected code.");

    const response = {
        tokens: {
            refresh_token: `abc${code}`,
            access_token: "def"
        },
        res: null
    }
    return Promise.resolve(response);
});


describe('Sample', function () {
    beforeEach(() => {
        jest.resetModules();
        jest.restoreAllMocks();
    });

    it('can get a token', async () => {
        const token = await accessToken();
        expect(token).toBeDefined();
        expect(oAuth2Client).toHaveBeenCalled();
    });
});

当我运行这个测试时，我会收到以下错误--这表示客户机正在尝试真正的调用。

Error: invalid_client

    at Gaxios._request (/Users/foo/dev/token-service/node_modules/gaxios/src/gaxios.ts:158:15)
    at processTicksAndRejections (internal/process/task_queues.js:95:5)
    at OAuth2Client.getTokenAsync (/Users/foo/dev/token-service/node_modules/google-auth-library/build/src/auth/oauth2client.js:124:21)
    at Object.accessToken (/Users/foo/dev/token-service/src/functions/sample.ts:7:22)
    at Object.<anonymous> (/Users/foo/dev/token-service/src/functions/sample.test.ts:29:23)

查看文件.. google-auth-library/build/src/auth/oauth2client.js，似乎TS转换程序输出了一个带有签名getToken(codeOrOptions, callback)的js函数，然后调用getTokenAsync。

我有点迷失在这里，我是不是在用jest.spy来嘲笑错误的过载？

Answer 1

我相信问题是：

const client: OAuth2Client = new OAuth2Client(
  "clientId", "clientSecret", "https://redirect.com"
);

而您实际上想要模拟的是prototype父对象。

const oAuth2Client = jest.spyOn(OAuth2Client.prototype, 'getToken') as unknown as jest.MockedFunction<GetTokenByCode>;

我将尝试以下几点：

• Nuke prototype在模拟
• 上查看是否可以避免通过依赖注入

在被测试系统中创建实例