Mocha Test: Uncaught TypeError: Cannot read property 'status' of null

Question

Learning TDD and my first simple test for my "Hello World" server response is failing in Mocha. I'm using Mocha.js, Superagent, & Expect.js.

When I curl -i localhost:8080, I get the correct response and status code.

HTTP/1.1 200 OK
Content-Type: text/plain
Date: Mon, 27 Apr 2015 17:55:36 GMT
Connection: keep-alive
Transfer-Encoding: chunked

Hello World

Test code:

var request = require('superagent');
var expect = require('expect.js');

// Test structure
describe('Suite one', function(){
    it("should get a response that contains World",function(done){
        request.get('localhost:8080').end(function(res){
            // TODO check that response is okay
            expect(res).to.exist;
            expect(res.status).to.equal(200);
            expect(res.body).to.contain('World');
            done();
        });
    });
});

Server code:

var server = require('http').createServer(function(req, res){
    res.writeHead(200, {"Content-Type":"text/plain"});
    res.end('Hello World\n');
});

server.listen(8080, function(){
    console.log("Server listening at port 8080");
});

Mocha output:

  Suite one
    1) should get a response that contains World


  0 passing (110ms)
  1 failing

  1) Suite one should get a response that contains World:
     Uncaught TypeError: Cannot read property 'status' of null
      at test.js:10:23
      at _stream_readable.js:908:16

I've tried googling this issue but no luck finding out what I'm doing wrong.

Solution

Node notation of callbacks is to have first parameter error.

Superagent is following this Node policy. This is from superagent github site:

request
  .post('/api/pet')
  .send({ name: 'Manny', species: 'cat' })
  .set('X-API-Key', 'foobar')
  .set('Accept', 'application/json')
  .end(function(err, res){
    // Calling the end function will send the request
  });

So change this line

request.get('localhost:8080').end(function(res){

to

request.get('localhost:8080').end(function(err, res){