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Website user interface regression testing



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.
    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.
    You can also add in additional settings:
        url= hasn't changed
    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)
    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/
        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
    Known Issues
    -  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
    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`` 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.



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