How do I mock my config file for testing?
<p>I have a Koa app I just started and I need to test something that grabs data from a config file.</p>

<p>I need to test with specific data, but I'm not sure how to modify what data the test receives from the config file.</p>

<p>Example:</p>

<p>app.js</p>

<pre><code>var router = require('koa-router');
var config = require('./config.js');
var db     = require('./db.js');
var auth   = require('./auth');
var app    = require('koa')();

router.get('/', function *() {
  if(auth(this.req, config.credentials.secret)) { // Authenticates request based on a hash created using a shared secret
    this.body = "Request has been authenticated";
  }
});

app.use(router.routes());
app = module.exports = http.createServer(app.callback());

app.listen(3000);
</code></pre>

<p>appSpec.js</p>

<pre><code>var request = require('supertest');
var app = require('../app.js');

describe('app', function() {
  it('should authenticate all requests against config shared secret', function() {
    var secret    = 'some_secret';
    var validHash = /* hash created from test secret and query */;

    request(app)
      .get('/')
      .query({query: 'some_query'})
      .query({hash: validHash})
      .expect(403, done);

  });
});
</code></pre>

<p>This spec will fail because the app will use the secret from the config file(empty string) instead of my test secret.</p>