How to test express middleware error handler with jest and TypeScript

I'm completely new to testing middleware with jest

The middleware

import HttpException from "../common/http-exception";  import { Request, Response, NextFunction } from "express";    export const errorHandler = (    error: HttpException,    request: Request,    response: Response,    next: NextFunction  ) => {    const status = error.statusCode || error.status || 500;      response.status(status).send(error);  };    

The broken test giving the error TypeError: Cannot read property 'send' of undefined

import HttpException from "../src/common/http-exception";  import { NextFunction, Request, Response, response } from "express";  import { errorHandler } from "../src/middleware/error.middleware";    describe("Error handler middleware", () => {    const error: HttpException = {      name: "error",      statusCode: 500,      status: 1,      message: "string",      error: "string"    };    let mockRequest: Partial<Request>;    let mockResponse: Partial<Response>;    let nextFunction: NextFunction = jest.fn();      beforeEach(() => {      mockRequest = {};      mockResponse = {        status: jest.fn()      };    });      test("handle error", async () => {      errorHandler(        error as HttpException,        mockRequest as Request,        mockResponse as Response,        nextFunction      );        expect(response).toBe(500);    });  });    

And the typescript for HttpException

export default class HttpException extends Error {    statusCode?: number;    status?: number;    message: string;    error: string | null;      constructor(statusCode: number, message: string, error?: string) {      super(message);        this.statusCode = statusCode;      this.message = message;      this.error = error || null;    }  }    

https://stackoverflow.com/questions/65893223/how-to-test-express-middleware-error-handler-with-jest-and-typescript January 26, 2021 at 06:20AM