Jest testing of async middleware for authentication - express

Question

I'm using a static array to scaffold a user table, prior to refactoring with actual postgres db and some fetch()-ing code. At present, the tests work, but obviously they are working synchronously. Here's the placeholder API code:
// UserAPI.js
let findUserById = (credentials = {}) => {
const { userId } = credentials
if (userId) {
const foundUser = users.find(user => user.id === userId)
if (foundUser !== undefined) {
const { password: storedpassword, ...user } = foundUser
return user
}
}
return null
}
exports.byId = findUserById
And an example test as follows:
// excerpt from TokenAuth.test.js
const UserAPI = require('../lib/UserAPI')
describe('With TokenAuth middleware', () => {
beforeEach(() => {
setStatus(0)
})
it('should add user to req on authorised requests', () => {
const token = createToken(fakeUser)
const authReq = { headers: { authorization: 'Bearer ' + token } }
const myMiddleware = TokenAuth(UserAPI.byId)
myMiddleware(authReq, fakeRes, fakeNext)
// expect(authReq.user).toStrictEqual({ id: 1, username: 'smith#example.com' });
expect(authReq.user.username).toStrictEqual('smith#example.com')
expect(authReq.user.id).toStrictEqual(1)
})
})
This runs fine, and along with other tests gives me the coverage I want. However, I now want to check that the tests will deal with the async/await nature of the fetch() code I'm going to use for the proper UserAPI.js file. So I re-write the placeholder code as:
// UserAPI.js with added async/await pauses ;-)
let findUserById = async (credentials = {}) => {
const { userId } = credentials
// simulate url resolution
await new Promise(resolve => setTimeout(() => resolve(), 100)) // avoid jest open handle error
if (userId) {
const foundUser = users.find(user => user.id === userId)
if (foundUser !== undefined) {
const { password: storedpassword, ...user } = foundUser
return user
}
}
return null
}
exports.byId = findUserById
... at which point I start getting some lovely failures, due I think it's returning unresolved promises.
My problem is two-fold:
How should I alter the UserAPI.test.js tests to deal with the new async nature of findUserByCredentials() ?
Am I ok in my assumption that ExpressJS is happy with async functions as request handlers? Specifically, due to the async nature ofUserAPI.findUserByCredentials is this ok?
Main App.js uses curried UserAPI.byId() for the findUserById.
// App.js (massively simplified)
const express = require('express')
const TokenAuth = require('./middleware/TokenAuth')
const RequireAuth = require('./middleware/RequireAuth')
const UserAPI = require('./lib/UserAPI')
let router = express.Router()
const app = express()
app.use(TokenAuth(UserAPI.byId))
app.use(RequireAuth)
app.use('/users', UserRouter)
module.exports = app
My TokenAuth middleware would now run along these lines:
// TokenAuth.js (simplified)
const jwt = require('jsonwebtoken')
require('dotenv').config()
const signature = process.env.SIGNATURE
let TokenAuth = findUserById => async (req, res, next) => {
let header = req.headers.authorization || ''
let [type, token] = header.split(' ')
if (type === 'Bearer') {
let payload
try {
payload = jwt.verify(token, signature)
} catch (err) {
res.sendStatus(401)
return
}
let user = await findUserById(payload)
if (user) {
req.user = user
} else {
res.sendStatus(401)
return
}
}
next()
}
module.exports = TokenAuth

Answer 1

A partial answer us simply to add an async/await on the middleware call:
it('should add user to req on authorised requests', async () => {
const token = createToken(fakeUser)
const authReq = { headers: { authorization: 'Bearer ' + token } }
const myMiddleware = TokenAuth(UserAPI.byId)
await myMiddleware(authReq, fakeRes, fakeNext)
// expect(authReq.user).toStrictEqual({ id: 1, username: 'smith#example.com' });
expect(authReq.user.username).toStrictEqual('smith#example.com')
expect(authReq.user.id).toStrictEqual(1)
})