Write a unit testing for a RestFul api Expressjs using mocha and superagent

spec-api.js

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

describe('express rest api server', function(){
  var id
  it('posts an object', function(done){
    superagent.post('http://localhost:3000/user/test')
    .send({ 
      name: 'Med',
      email: '[email protected]'
    })
    .end(function(e,res){
      // console.log(res.body)
      expect(e).to.eql(null)
      expect(res.body.length).to.eql(1)
      expect(res.body[0]._id.length).to.eql(24)
      id = res.body[0]._id
      done()
    })
  })
});