Poltergeist - A PhantomJS driver for Capybara

Version: 0.2.0

Poltergeist is a driver for Capybara. It allows you to run your Capybara tests on a headless WebKit browser, provided by PhantomJS.

Installation

Add poltergeist to your Gemfile, and add in your test setup add:

require 'capybara/poltergeist'
Capybara.javascript_driver = :poltergeist

Currently PhantomJS is not 'truly headless', so to run it on a continuous integration server you will need to use Xvfb. You can either use the headless gem for this, or make sure that Xvfb is running and the DISPLAY environment variable is set.

Installing PhantomJS

You need PhantomJS 1.4.1+, built against Qt 4.8, on your system.

Mac users

By far the easiest, most reliable thing to do is to install the pre-built static binary. Try this first.

Linux users, or if the pre-built Mac binary doesn't work

You need to build PhantomJS manually. Unfortunately, this not currently straightforward, for two reasons:

1. Using Poltergeist with PhantomJS built against Qt 4.7 causes segfaults in WebKit's Javascript engine. Fortunately, this problem doesn't occur under the recently released Qt 4.8. But if you don't have Qt 4.8 on your system (check with qmake --version), you'll need to build it.

2. A change in the version of WebKit bundled with Qt 4.8 means that in order to be able to attach files to file <input> elements, we must apply a patch to the Qt source tree that PhantomJS is built against.

So, you basically have two options:

1. If you have Qt 4.8 on your system, and don't need to use file inputs, follow the standard PhantomJS build instructions.

2. Otherwise, download the PhantomJS tarball and run either deploy/build-linux.sh --qt-4.8 or cd deploy; ./build-mac.sh. The script will download Qt, apply some patches, build it, and then build PhantomJS against the patched build of Qt. It takes quite a while, around 30 minutes on a modern computer with two hyperthreaded cores. Afterwards, you should copy the bin/phantomjs binary into your PATH.

PhantomJS 1.5 plans to bundle a stripped-down version of Qt, which will reduce the build time a bit (although most of the time is spent building WebKit) and make it easier to apply patches. When it is possible to make static builds for Linux, those may be provided too, so most users will avoid having to build it themselves.

What's supported?

Poltergeist supports basically everything that is supported by the stock Selenium driver, including Javascript, drag-and-drop, etc.

There are some additional features:

Taking screenshots

You can grab screenshots of the page at any point by calling page.driver.render('/path/to/file.png') (this works the same way as the PhantomJS render feature, so you can specify other extensions like .pdf, .gif, etc.)

By default, only the viewport will be rendered (the part of the page that is in view). To render the entire page, use page.driver.render('/path/to/file.png', :full => true).

Resizing the window

Sometimes the window size is important to how things are rendered. Poltergeist sets the window size to 1024x768 by default, but you can set this yourself with page.driver.resize(width, height).

Customization

You can customize the way that Capybara sets up Poltegeist via the following code in your test setup:

Capybara.register_driver :poltergeist do |app|
  Capybara::Poltergeist::Driver.new(app, options)
end

options is a hash of options. The following options are supported:

• :phantomjs (String) - A custom path to the phantomjs executable
• :debug (Boolean) - When true, debug output is logged to STDERR
• :logger (Object responding to puts) - When present, debug output is written to this object

Bugs

Please file bug reports on Github and include example code to reproduce the problem wherever possible. (Tests are even better.) Please also provide the output with :debug turned on, and screenshots if you think it's relevant.

Why not use capybara-webkit?

If capybara-webkit works for you, then by all means carry on using it.

However, I have had some trouble with it, and Poltergeist basically started as an experiment to see whether a PhantomJS driver was possible. (It turned out it was, but only thanks to some new features since the 1.3 release.)

In the long term, I think having a PhantomJS driver makes sense, because that allows PhantomJS to concentrate on being an awesome headless browser, while the capybara driver (Poltergeist) is able to be the minimal amount of glue code necessary to drive the browser.

I also find it more pleasant to hack in CoffeeScript than C++, particularly as my C++ experience only goes as far as trying to make PhantomJS/Qt/WebKit work with Poltergeist :)

Hacking

Contributions are very welcome and I will happily give commit access to anyone who does a few good pull requests.

To get setup, run bundle install. You can run the full test suite with rspec spec/ or rake.

I previously set up the repository on Travis CI but unfortunately given they need a custom-built Qt+PhantomJS in order to pass, it can't be used for now. When static Linux PhantomJS builds are working this can be revisited.

While PhantomJS is capable of compiling and running CoffeeScript code directly, I prefer to compile the code myself and distribute that (it makes debugging easier). Running rake autocompile will watch the .coffee files for changes, and compile them into lib/capybara/client/compiled.

License

Copyright (c) 2011 Jonathan Leighton

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.