expresso -> mocha

expressoSession.js

var
  app = require(__dirname + '/../app'),

exports.testGetSessionValid = function (beforeExit, assert) {

  assert.response(app, {
    url: '/api/getSession/apikey',
    method: 'GET',
    headers: { 'Content-Type': 'text/html; charset=utf-8' }
  }, {
    status: 200,
    headers: { 'Content-Type': 'application/json; charset=utf-8' }
  },
  function(res) {
    var json = JSON.parse(res.body);

    assert.isDefined(json.sess);
    assert.equal(json.userId, 0);
  }
  );
};

mocha_test.sh

#!/bin/bash
# Mocha tests starter
mocha -R list -u exports test/mochaSession.js
exit 0

mochaSession.js

var
  app = require(__dirname + '/../app'),
  supertest = require('supertest'),
  should = require('should');

exports.testGetSessionValid = {
  'GET /api/getSession/:apikey': {
    'should return valid json response with sess and userId property': function (done){
      supertest(app)
      .get('/api/getSession/apikey')
      .expect('Content-Type', 'application/json; charset=utf-8')
      .expect(200)
      .end(function (err, res) {

        if (err) {
          done(err);
        }

        try {
          res.body.should.have.property('sess');
          res.body.should.have.property('userId');
          res.body.userId.should.equal(0);
          done();
        }
        catch (e) {
          done(e);
        }
      });
    }
  }
};

Gist shows how to fast switch from expresso to mocha "response" testing (expressoSession.js -> mochaSession.js)