expressjs - res.status is not a function TypeError

Hello,

I used supertest with tape, sinon, proxyquire & expressJS, I got this error :

error: res.status is not a function TypeError: res.status is not a function
    at <path>\index.ts:26:11
    at process._tickDomainCallback (internal/process/next_tick.js:129:7)
(node:21020) UnhandledPromiseRejectionWarning: Unhandled promise rejection (rejection id: 1): TypeError: res.sendStatus is not a function

this is my route function

router.get('/customers', middleware, (req: express.Request, res: express.Response) => {
  let options = {
    uri: url,
    method: 'GET',
  };
  request(req, options).then(body => {
    if (body) {
      res.status(200).send(body);
    }
  }).catch((error) => {
    res.sendStatus(500);
  });
});

my unit test

import * as test from 'tape';
import * as sinon from 'sinon';
import * as request from 'supertest';
import * as proxyquire from 'proxyquire';

const requestStub = sinon.stub();

const stubResponse = {
  statusCode: 200,
  body: { body: 'body' }
};

const api = proxyquire('./', { 'api-request': requestStub });
requestStub.returns(Promise.resolve(stubResponse));

test('Get /customers', (assert) => {

  const agent = request.agent(api);

  agent
    .get('/customers')
    .expect(200)
    .set('Accept', 'application/json')
    .end((err, res) => {
      var expectedThings =
        {
          "some" : "data"
        };
      var actualThings = res.body;

      assert.error(err, 'No error');
      assert.same(actualThings, expectedThings, 'Retrieve list of things');
      assert.end();
    });
});

Do you have any idea?

[iLyxa3D]

Fixed, in my case… Just add “next” to the variables list (err, req, res, next)

app.use((err, req, res, next) => { console.error(err); res.status(500).json({error: 'an error occurred'}); });

From documentation: https://expressjs.com/ru/api.html

Error-handling middleware always takes four arguments. You must provide four arguments to identify it as an error-handling middleware function. Even if you don’t need to use the next object, you must specify it to maintain the signature. Otherwise, the next object will be interpreted as regular middleware and will fail to handle errors.

[nikhedonia]

I encountered the same error when applying supertest on a express route.

const routes = express.Router();
routes.get('/', ()=> res.status(200).send('blub'))
request(routes).get('/').end() // status not a function
request(app.use(routes)).get('/').end() // works