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NOTE: Blue Ridge is no longer officially supported by Relevance. We recommend you check out Jasmine by Pivotal Labs instead.

Blue Ridge JavaScript Testing Rails Plugin

The Blue Ridge JavaScript Testing Rails Plugin adds support for command-line and in-browser JavaScript unit tests to your Rails app. It bundles several great tools together in a convention-over-configuration, Rails-like way. These tools include:

  • Rhino - a Java-based JavaScript interpreter
  • Screw.Unit - a behaviour-driven development syntax for JavaScript similar to RSpec
  • Smoke - a JavaScript mocking & stubbing library similar to Mocha
  • env.js - a DOM implementation written entirely in JavaScript

Please join our mailing list if you're interested in Blue Ridge!

Installing and Running

To install:

./script/plugin install git://
./script/generate blue_ridge

To run all of the specs:

rake test:javascripts

(Hint: You can also use the spec:javascripts or examples:javascripts aliases.)

To run an individual spec file called "application_spec.js":

rake test:javascripts TEST=application

To generate and run a spec for a JavaScript file called "public/javascripts/graphics.js" run:

./script/generate javascript_spec graphics
rake test:javascripts TEST=graphics

To run your spec inside a web browser, load the HTML fixture associated with the spec. (See below for more information on HTML fixtures and in-browser testing).

Directory Layout: Specs and Fixtures

JavaScript Spec Directories

Blue Ridge creates a directory for your JavaScript specs in one of the following directories, depending on which tool you use to test your Ruby code:

  • examples/javascripts: if you're using Micronaut
  • spec/javascripts: if you're using RSpec
  • test/javascript: if you're using anything else

The layout of the JavaScript spec directories looks like this (assuming you created a "graphics" spec as described in the section above):

"javascripts" directory

  • application_spec.js: file with Screw.Unit specs; intended for testing code in public/javascripts/application.js
  • graphics_spec.js: another spec file; intended for testing code in public/javascripts/graphics.js
  • spec_helper.js: a place a you to store your common configuration & convenience functions; auto-included by each spec

"javascripts/fixtures" directory

  • application.html: base DOM for application_spec.js; also runs specs in-browser
  • graphics.html: base DOM for graphics_spec.js; also runs specs in-browser
  • screw.css: stylesheet for Screw.Unit output when running specs in-browser

Why We Need Fixtures

Blue Ridge relies on the convention that each spec file will have a similarly named HTML file in the fixtures directory. We create one fixture per spec file so that env.js has a base DOM to emulate when running specs from the command line and so that we have an HTML launch-pad to run our specs in-browser.

If you want to have specific HTML for a suite of specs, put it in the HTML fixture for that suite. If you want to run a specific suite of tests in Firefox or Internet Explorer, open the HTML fixture file with the same name and Screw.Unit automatically runs the specs associated with the fixture.

Example Using jQuery

Blue Ridge is opinionated and assumes you're using jQuery by default. The plugin itself actually uses jQuery under the covers to run Screw.Unit.


Screw.Unit(function() {
  describe("Your application javascript", function() {
    it("does something", function() {
      expect("hello").to(equal, "hello");

    it("accesses the DOM from fixtures/application.html", function() {
      expect($('.select_me').length).to(equal, 2);

(By the way, we don’t actually encourage you to write specs and tests for standard libraries like JQuery and Prototype. It just makes for an easy demo.)

Example Using Prototype

It's very easy to add support for Prototype. Here's an example spec:


require("../../public/javascripts/prototype.js", {onload: function() {

Screw.Unit(function() {
    describe("Your application javascript", function() {
        it("does something", function() {
            expect("hello").to(equal, "hello");

        it("accesses the DOM from fixtures/application.html", function() {
            expect($$('.select_me').length).to(equal, 2);

Note that you must do the following:

  • put jQuery into "no conflict" mode to give the $ function back to Prototype
  • require the prototype.js file
  • chain any files that are dependent on prototype.js in the onload callback

More Examples

To see Blue Ridge in action inside a working Rails app, check out the Blue Ridge sample application. Among other things, this sample app includes examples of:

  • using nested describe functions
  • setting up per-spec HTML "fixtures"
  • stubbing functions
  • mocking functions
  • running the Blue Ridge specs as part of your default Rake task

JavaScript API

The Blue Ridge plugin provides a handful of functions that help you write specs that run correctly inside a web browser as well from the Rhino command-line test runner.

require(fileName, [{onload:function}])

When running from the command line, require becomes a Rhino call to load. In a web browser, require dynamically creates a JavaScript script tag and loads the given file for you. It takes an optional onload callback function that runs immediately after the given JavaScript file is loaded. This helps you chain dependencies. This is especially useful when running in-browser where each JavaScript file is loaded asynchronously in a separate thread.

require("../../public/javascripts/prerequisite.js", {onload: function() {


When running from the command line, debug simply prints a message to stdout, but in a web browser it outputs into the DOM directly. This helps you avoid using the print function which prints to stdout in Rhino but actually opens a file print dialog when running in a browser!


If you use Firebug, you might add a console.debug function call in your tests to debug a problem. Calling this from the command-line would crash, however, because Firebug is missing. To make life a little easier, this console.debug function is just an alias to Rhino's print function and will write your message to stdout.


rake js:fixtures

If you're on Mac OS X, this command opens your JavaScript fixtures directory using Finder so you can quickly locate and open any spec that you want to run in the browser. If you're running on Linux, it opens the fixtures directory using Firefox.

rake js:shell

Runs an IRB-like JavaScript shell for debugging your JavaScript code. jQuery and env.js are pre-loaded for you to make debugging DOM code easy.

rake js:shell

 Rhino JavaScript Shell
 To exit type 'exit', 'quit', or 'quit()'.
 - loaded env.js
 - sample DOM loaded
 - jQuery-1.2.6 loaded
Rhino 1.7 release 2 PRERELEASE 2008 07 28
js> print("Hello World!")
Hello World!

Note that if you have rlwrap installed and on the command line path (and you really, really should!), then command-line history and readline arrow-up and down will be properly supported automatically. (You can get rlwrap from your friendly neighborhood package manager.)

Mocking Example with Smoke

Smoke is a JavaScript mocking and stubbing toolkit that is somewhat similar to FlexMock or Mocha. It is automatically wired-in to undo its mocking after each Screw.Unit it block. Here's an example.

it("calculates the total cost of a contract by adding the prices of each component", function() {
  var componentX = {}, componentY = {};
  mock(SalesContract).should_receive("calculateComponentPrice").with_arguments(componentX).exactly(1, "times").and_return(42);
  mock(SalesContract).should_receive("calculateComponentPrice").with_arguments(componentY).exactly(1, "times").and_return(24);
  expect(SalesContract.calculateTotalCost([componentX, componentY])).to(equal, 66);

TextMate Integration

Run your specs directory from TextMate using the Blue Ridge TextMate Bundle. (It's a fork of the original Screw.Unit TextMate Bundle but adapted for use with the Blue Ridge plugin.)

cd ~/Library/Application Support/TextMate/Bundles/
git clone git:// Blue\ Ridge.tmbundle

Then when editing a Screw.Unit spec file in TextMate you can:

  • press command-R to run the spec directly from TextMate
  • type snippets like "it", "des", "bef", "aft" and then press the tab key to expand into full it blocks, describe blocks, etc.

Tips & Tricks

  • Avoid using print in your tests while debugging. It works fine from the command line but causes lots of headaches in browser. (Just imagine a print dialog opening ten or fifteen times and then Firefox crashing. This is a mistake I've made too many times! Trust me!)
  • We don't recommend testing jQuery or Prototype, especially event wiring. (You don't test Rails, do you?) Instead write a separate function, test it, and wire it to events using jQuery or Prototype.

Bugs & Patches

First, if you see any bugs or possible improvements, please use the project's GitHub issue tracker to let us know about them.

But even better, fork our GitHub repo and start hacking! If you have patches, send us pull requests. Also, env.js, Smoke, and Screw.Unit could use your love too!



  • Copyright © 2008-2009 Relevance, Inc., under the MIT license
  • env.js - Copyright 2007-2009 John Resig, under the MIT License
  • Screw.Unit - Copyright 2008 Nick Kallen, license attached
  • Rhino - Copyright 2009 Mozilla Foundation, GPL 2.0
  • Smoke - Copyright 2008 Andy Kent, license attached