Faking the time for tests' sake

gistfile1.js

// app/assets/env/test/time.js
window.__rails_test_time = Date();
// Or for you CS guys
@.__rails_test_time = Date()

In your JS that uses a cached Time.now-style date object, use this for assignment:
var now = window.__rails_test_time || Date();

Then conditionally include your test JS like so:
= javascript_include_tag "env/test/time" if Rails.env.test?
//        .-.
//        |U|
//        | |
//        | |-._
//        | | | |-.
//       /|     ` |
//      | |       |   LIKE
//      |         |      SO:
//      \         /
//       |       |
//       |       |