Gossamer
========

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.

Features
--------

-  Supports JavaScript, including single-page apps
-  Allows navigating to new pages
-  Records your clicks and text input
-  Supports setting cookies for authentication and settings
-  During playback, waits for the page to be stable before taking
   further actions, rather than deciding on the basis of time elapsed
-  Tests can be run alongside your other Python ``unittest`` tests.
   Populate a module with a ``unittest.TestCase`` for each test within a
   testfile by calling
   ``run_gossamerfile(locals(), <filename>, <data_dir>)``. You can run
   it on your dev machine without worrying about Selenium when you don't
   need it, because Gossamer's tests skip by default if Selenium isn't
   running.
-  Configurable browser, data directories, and settings
-  Data is exported and read on every run as regular JSON files and PNGs

Usage
-----

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 windowis 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

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.

::

    gossamer --file Gossamerfile --data <data_dir> --record --save-diff example

**When you browse, wait for requests to finish and rendering to be
complete before moving on to another action.** Also, scrolling is
currently unreliable and best avoided. If you work within those
limitations, playback will be reliable.

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.

::

    gossamer --file Gossamerfile --data <data_dir> --rerecord

To playback the tests, simply call without an ``-r/-rr`` flag:

::

    gossamer --file Gossamerfile --data <data_dir>

Further command-line options:

::

    --browser/-b: browser to use
    --save-diff/-e: when two images don't match, save a diff.png which
    highlights pixels that differ
    --overwrite/-o: when recording tests, don't prompt about overwriting data
    --local/-l: URL to Selenium.

Command-line options take precedence over Gossamerfile options. During
playback, command-line or Gossamerfile options affecting the test itself
are ignored; only the Selenium server to test against and data directory
can be changed.

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 populates your module's locals with 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.

Installation
------------

Your testing machine will need
`Pillow's <https://github.com/python-imaging/Pillow>`__ system-level
dependencies for PNG support (namely ``zlib1g-dev``, on Ubuntu, and
Python dev). Gossamer can then be installed from PyPi with
``pip install gossamerui``.

On that machine or another accessible to it you will need `Selenium
Server <http://docs.seleniumhq.org/download/>`__ 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.

Authors
-------

See the file ``AUTHORS``. Based on Facebook's
`Huxley <https://github.com/facebook/huxley>`__, and rewritten.

License
-------

Apache 2.0

Known Issues
------------

-  Need support for changing the test URL via CLI and
   ``run_gossamerfile`` to support different environments.
-  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``).

Issues
------

Please create issues and pull requests at the `GitHub
repository <https://github.com/ijl/gossamer>`__.

Contributing
------------

-  Once you have the repository, setup using ``make develop``.
-  Please add tests and use the included .pylintrc; you can run
   ``make test`` and ``make lint``.
-  If any breaking changes are made to data structures, increment
   ``constant.DATA_VERSION`` and modify ``util.import_recorded_run`` to
   handle both new and old data.
-  Feel free to contribute any functionality you want.

