import { Request, Response, Router } from "express";
import * as redis from "redis";
const redisOption: redis.ClientOpts = {
    host: "13.125.255.140",
    port: 6379,
    detect_buffers : true,
    db: 0,
   retry_strategy: () => 60000
}
const redisClient: redis.RedisClient = redis.createClient(redisOption);

export class IndexRoutes {
    public router: Router;
    constructor() {
        this.router = Router();
        this.init();
    }
    public init() {
        this.router.get("/",  this.getFunc);
    }
    private getFunc = async (req: Request, res: Response) => {
        return res.status(200).send(await redisClient.set("test", "123"));
    }
}

import * as redis from 'redis';

describe('my redis wrapper', () => {
  it('Should call get when my wrapper's getFunc is called', () => {
    let myRedisSpy = jest.spyOn(redis.prototype, 'get');
    // call your function here
    expect(myRedisSpy).toHaveBeenCalledOnce();
  });
});