Gossamer watches you browse a website and record screenshots of your UI, then recreates your browsing session and passes or fails tests depending on whether the UI has changed. It's a way of automating in-browser visual regression testing, using Gossamer to automate Selenium WebDriver, expose test statuses of pass/fail/error, and provide visual diffs of failing tests. You needn't write Selenium tests, or make and keep in sync static pages for testing UI: this tool will test full webpages run on a development or testing webserver. Gossamer can be integrated into your continuous integration either via the command-line interface, or, if you're testing a Python application, via Python unittest integration.
Gossamer is a command-line application, called with gossamer
. You create
tests you wish to record in a text Gossamerfile. For each test, a WebDriver
window is opened and you interact with the browser as a normal user, going
back to the command line when you wish to take a screenshot and pressing
enter. Your screenshots, and a JSON record of your test, is written to a
data directory. Playback is done by reading this directory, and comparing
against 'good' screenshots. Gossamer assumes that Selenium Server is
already running.
To start, create a file Gossamerfile
and specify a name and URL to visit for
every test.
[example]
url=http://www.example.com
You can also add in additional settings:
[example]
url=http://www.example.com
desc=Example.com hasn't changed
screensize=800x1000
browser=chrome
expect_redirect=false
By default, Gossamer looks for a file called Gossamerfile
in the current
directory, and stores data in ./gossamer
with one directory per test. Each
test directory contains a record.json
containing the data to reproduce the
test, as well as good screenshots, and in a sub-directory last
, the
last test run's (possibly failing) screenshots.
You can run your tests with:
gossamer --file Gossamerfile --data <data_dir> --record --save-diff
If you wish to run only a subset of tests in that file, specify those tests' names as positional arguments.
When you browse, wait for requests to finish and rendering to be complete before moving on to another action. If you navigate to a new page, you will need to take a screenshot before new events are observed.
If your UI has changed and you wish to update the screenshots to match, then
run with --rerecord
: the test will be rerun automatically, and new PNGs
will be saved. To playback the tests, simply call without an -r/-rr
flag.
If you're running Python tests, you can integrate your Gossamer tests like so:
# myapp/test.py
from gossamer import run_gossamerfile
run_gossamerfile(locals(), <filename>, <data_dir>)
This mutates your module's locals to include a unittest.TestCase
instance
for every test in the given Gossamerfile(s). Your test runner will then
detect and run them. You will, however, need to ensure that your Selenium
server and test webserver are up when your tests are run.
Your testing machine will need
Pillow's system-level
dependencies for PNG support. Gossamer can then be installed from PyPi with pip install gossamerui
.
On that machine or another accessible to it you will need Selenium Server installed and running. Note that Selenium Server comes with Firefox by default, needing an additional system package for Chrome, and for Internet Explorer an IE-specific standalone version of Selenium Server.
You'll also need your 'target' webserver running on any machine.
See the file AUTHORS
. Based on Facebook's
Huxley, and rewritten.
Apache 2.0
- Scrolling is unreliable.
- Opening a slow iframe will likely timeout on playback.
- Internet Explorer < 11 (which is all Selenium supports) shouldn't work at
the moment because we use MutationObservers, but an older way of observing
changes can be added for IE<11 (see
js.pageChangingObserver
).
Please create issues and pull requests at the GitHub repository.
- Once you have the repository, setup using
make develop
. - Please add tests and use the included .pylintrc; you can run
make test
andmake lint
. - If any breaking changes are made to data structures, increment
constant.DATA_VERSION
and modifyutil.import_recorded_run
to handle both new and old data. - Feel free to contribute any functionality you want.