Testing binary downloads using chai-http

bin-test.spec.ts

import 'mocha';
import { expect, request } from 'chai';
import chaiHttp = require('chai-http');

import { app } from '../../server';

chai.use(chaiHttp);

const BIN_FILE = new Buffer([
  0x50, 0x4b, 0x05, 0x06, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
]);

describe('binary download should work', () => {
  let r : ChaiHttp.Response;

  before(async() => {
    r = await request(app)
        .get(`/download`)
        .buffer().parse(binaryParser);
  });

  it('should return HTTP 200: OK', () => {
    expect(r.status).to.equal(200);
  });

  it('should return the binary data correctly', () => {
    expect(r.body).to.deep.equal(BIN_FILE);
  });
});

// Source: https://stackoverflow.com/a/14802413/292586
function binaryParser(res : any, cb : (e? : Error, r? : any) => void) {
  let data = '';
  res.setEncoding('binary');
  res.on('data', function(chunk : any) { data += chunk; });
  res.on('end', function() { cb(undefined, new Buffer(data, 'binary')); });
}