Poltergeist - A PhantomJS driver for Capybara
poltergeist to your Gemfile, and in your test setup add:
Important note about Rack versions < 1.3.0
Prior to version 1.3.0, the Rack handlers for Mongrel and Thin wrap your
app in the
Rack::Chunked middleware so that it uses
This has been observed to cause problems,
probably due to race conditions in Qt's HTTP handling code, so you are
recommended to avoid this by specifying your own server setup for
Capybara.server do |app, port| require 'rack/handler/thin' Thin::Logging.silent = true Thin::Server.new('0.0.0.0', port, app).start end
If you're using Rails 3.0, this affects you. If you're using Rails 3.1+, this doesn't affect you.
You need PhantomJS 1.4.1+, built against Qt 4.8, on your system.
There are pre-built binaries of PhantomJS for Linux, Mac and Windows. This is the easiest and best way to install it. The binaries including a patched version of Qt 4.8 so you don't need to install that separately.
Note that if you have a 'dynamic' package, it's important to maintain
the relationship between
lib/. This is because the
bin/phantomjs binary looks in
../lib/ for its library files. So the
best thing to do is to link (rather than copy) it into your
ln -s /path/to/phantomjs/bin/phantomjs /usr/local/bin/phantomjs
If you're having trouble with a pre-built binary package, you can compile PhantomJS yourself. PhantomJS must be built against Qt 4.8, and some patches must be applied, so note that you cannot build it against your system install of Qt.
Download the 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 (or link) the
bin/phantomjs binary into your
Running on a CI
Currently PhantomJS is not yet 'truly headless' (but that's planned for the future), so to run it on a continuous integration server you will need to install Xvfb.
On any generic server
Install PhantomJS and invoke your tests with
Travis CI has PhantomJS installed already! So all you need to do is add
the following to your
before_script: - "export DISPLAY=:99.0" - "sh -e /etc/init.d/xvfb start"
There are some additional features:
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
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
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
:logger(Object responding to
puts) - When present, debug output is written to this object
:timeout(Numeric) - The number of seconds we'll wait for a response when communicating with PhantomJS.
nilmeans wait forever. Default is 30.
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.
Poltergeist is similar to capybara-webkit, but here are the key differences:
It's more hackable. Poltergeist is written in Ruby + CoffeeScript. We only have to worry about C++ when dealing with issues in PhantomJS itself. In contrast, the majority of capybara-webkit is written in C++.
We're able to tap into the PhantomJS community. When PhantomJS improves, Poltergeist improves. User's don't have to install Qt because self-contained PhantomJS binary packages are available.
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
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
Detect if clicking an element will fail. If the click will actually hit another element (because that element is in front of the one we want to click), the user will now see an exception explaining what happened and which element would actually be targeted by the click. This should aid debugging. [Issue #25]
Click elements at their middle position rather than the top-left. This is presumed to be more likely to succeed because the top-left may be obscured by overlapping elements, negative margins, etc. [Issue #26]
Add experimental support for using the remote WebKit web inspector. This will only work with PhantomJS 1.5, which is not yet released, so it won't be officially supported by Poltergeist until 1.5 is released. [Issue #31]
page.driver.quitmethod. If you spawn additional Capybara sessions, you might want to use this to reap the child phantomjs process. [Issue #24]
Fix bug where we could end up interacting with an obsolete element. [Issue #30]
Raise an suitable error if PhantomJS returns a non-zero exit status. Previously a version error would be raised, indicating that the PhantomJS version was too old when in fact it did not start at all. [Issue #23]
:timeoutoption is actually used. [Issue #36]
In some circumstances, we could end up missing an inline element when attempting to click it. This is due to the use of
getBoundingClientRect(). We're now using
getClientRects()to address this.
Element click position is now calculated using the native
getBoundingClientRect()method, which will be faster and less buggy.
window.confirm(). Always returns true, which is the same as capybara-webkit. [Issue #10]
window.prompt(). Returns the default value, if present, or null.
There was a bad bug to do with clicking elements in a page where the page is smaller than the window. The incorrect position would be calculated, and so the click would happen in the wrong place. This is fixed. [Issue #8]
Poltergeist didn't work in conjunction with the Thin web server, because that server uses Event Machine, and Poltergeist was assuming that it was the only thing in the process using EventMachine.
To solve this, EventMachine usage has been completely removed, which has the welcome side-effect of being more efficient because we no longer have the overhead of running a mostly-idle event loop.
:timeoutoption to configure the timeout when talking to PhantomJS.
- First version considered 'ready', hopefully fewer problems.
- First version, various problems.
Copyright (c) 2011 Jonathan Leighton
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