How create a unit test a express middleware writed in typescript with jest

middleware.spec.ts

import { Application, Request, Response, NextFunction, RequestHandler } from 'express'

describe('How to test a express middleware', () => {
  const simpleMiddleware: RequestHandler = (req, res) => {
    return res.status(200).json({ 
      message: `App running at http://localhost:${req.app.locals.config.port}`
    })
  }
  
  const mockApp: Partial<Application> = {
    locals: {
      config: {
        port: 8000
      }
    }
  }

  const mockRequest: Partial<Request> = {
    app: mockApp as Application
  }

  const mockResponse: Partial<Response> = {
    json: jest.fn().mockImplementation(() => mockResponse),
    status: jest.fn().mockImplementation(() => mockResponse),
  }

  const mockNext = jest.fn() as jest.Mocked<NextFunction>

  it('should run correctly', () => {
    simpleMiddleware(mockRequest as Request, mockResponse as Response, mockNext)
    expect(mockResponse.status).toHaveBeenCalledTimes(1)
    expect(mockResponse.status).toHaveBeenCalledWith(200)
    expect(mockResponse.json).toHaveBeenCalledTimes(1)
    expect(mockResponse.json).toHaveBeenCalledWith({
      message: 'App running at http://localhost:8000'
    })
  })
})