Simple Koa Context for testing in Typescript (Mocha-chai, Jest) etc

koa-context.ts

/* eslint-disable @typescript-eslint/ban-ts-comment */
// @ts-nocheck

// Ripped from https://github.com/koajs/koa/blob/master/test/helpers/context.js
// Solution courtesy of user @fl0w. See: https://github.com/koajs/koa/issues/999#issuecomment-309270599
// I've disabled type checking in this file but you are free to add types if you wish

// if you want more comprehensive Koa Context object to test stuff like Cookies etc
// then use https://www.npmjs.com/package/@shopify/jest-koa-mocks (requires Jest)

// INSTRUCTIONS:
// Import in test file as below:
//
// import { context } from './koa-context'
// const ctx = context()
// ...

import Stream from 'stream'
import Koa from 'koa'

export const context = (req?, res?, app?) => {
    const socket = new Stream.Duplex()

    req = Object.assign({ headers: {}, socket }, Stream.Readable.prototype, req || {})
    res = Object.assign({ _headers: {}, socket }, Stream.Writable.prototype, res || {})
    req.socket.remoteAddress = req.socket.remoteAddress || '127.0.0.1'
    app = app || new Koa()
    res.getHeader = (k) => res._headers[k.toLowerCase()]
    res.setHeader = (k, v) => (res._headers[k.toLowerCase()] = v)
    res.removeHeader = (k, v) => delete res._headers[k.toLowerCase()]

    return app.createContext(req, res)
}

export const request = (req, res, app) => context(req, res, app).request

export const response = (req, res, app) => context(req, res, app).response

Thanks! pretty useful, but still struggling with mocking GET request and 'query' parameter

Sorry, my bad. I found existing unit-test for query parameters: https://github.com/koajs/koa/blob/e9494b5b3e040e4427710649f28b6cfa3b3ae845/__tests__/request/query.js

Well, it worked like a charm!