python-pytest-doc 2.6.3-2 / usr / share / doc / python-pytest-doc / html / _sources / plugins.txt

.. _plugins:

Working with plugins and conftest files
=============================================

``pytest`` implements all aspects of configuration, collection, running and reporting by calling `well specified hooks`_.  Virtually any Python module can be registered as a plugin.  It can implement any number of hook functions (usually two or three) which all have a ``pytest_`` prefix, making hook functions easy to distinguish and find.  There are three basic location types:

* `builtin plugins`_: loaded from pytest's internal ``_pytest`` directory.
* `external plugins`_: modules discovered through `setuptools entry points`_
* `conftest.py plugins`_: modules auto-discovered in test directories

.. _`pytest/plugin`: http://bitbucket.org/hpk42/pytest/src/tip/pytest/plugin/
.. _`conftest.py plugins`:
.. _`conftest.py`:
.. _`localplugin`:
.. _`conftest`:

conftest.py: local per-directory plugins
--------------------------------------------------------------

local ``conftest.py`` plugins contain directory-specific hook
implementations.  Session and test running activities will
invoke all hooks defined in ``conftest.py`` files closer to the
root of the filesystem.  Example: Assume the following layout
and content of files::

    a/conftest.py:
        def pytest_runtest_setup(item):
            # called for running each test in 'a' directory
            print ("setting up", item)

    a/test_in_subdir.py:
        def test_sub():
            pass

    test_flat.py:
        def test_flat():
            pass

Here is how you might run it::

     py.test test_flat.py   # will not show "setting up"
     py.test a/test_sub.py  # will show "setting up"

.. Note::
    If you have ``conftest.py`` files which do not reside in a
    python package directory (i.e. one containing an ``__init__.py``) then
    "import conftest" can be ambiguous because there might be other
    ``conftest.py`` files as well on your PYTHONPATH or ``sys.path``.
    It is thus good practise for projects to either put ``conftest.py``
    under a package scope or to never import anything from a
    conftest.py file.

.. _`external plugins`:
.. _`extplugins`:

Installing External Plugins / Searching
------------------------------------------------------

Installing a plugin happens through any usual Python installation
tool, for example::

    pip install pytest-NAME
    pip uninstall pytest-NAME

If a plugin is installed, ``pytest`` automatically finds and integrates it,
there is no need to activate it.  We have a :doc:`page listing
all 3rd party plugins and their status against the latest py.test version
<plugins_index/index>` and here is a little annotated list
for some popular plugins:

.. _`django`: https://www.djangoproject.com/

* `pytest-django <http://pypi.python.org/pypi/pytest-django>`_: write tests
  for `django`_ apps, using pytest integration.

* `pytest-twisted <http://pypi.python.org/pypi/pytest-twisted>`_: write tests
  for `twisted <http://twistedmatrix.com>`_ apps, starting a reactor and
  processing deferreds from test functions.

* `pytest-capturelog <http://pypi.python.org/pypi/pytest-capturelog>`_:
  to capture and assert about messages from the logging module

* `pytest-cov <http://pypi.python.org/pypi/pytest-cov>`_:
  coverage reporting, compatible with distributed testing

* `pytest-xdist <http://pypi.python.org/pypi/pytest-xdist>`_:
  to distribute tests to CPUs and remote hosts, to run in boxed
  mode which allows to survive segmentation faults, to run in
  looponfailing mode, automatically re-running failing tests
  on file changes, see also :ref:`xdist`

* `pytest-instafail <http://pypi.python.org/pypi/pytest-instafail>`_:
  to report failures while the test run is happening.

* `pytest-bdd <http://pypi.python.org/pypi/pytest-bdd>`_ and
  `pytest-konira <http://pypi.python.org/pypi/pytest-konira>`_
  to write tests using behaviour-driven testing.

* `pytest-timeout <http://pypi.python.org/pypi/pytest-timeout>`_:
  to timeout tests based on function marks or global definitions.

* `pytest-cache <http://pypi.python.org/pypi/pytest-cache>`_:
  to interactively re-run failing tests and help other plugins to
  store test run information across invocations.

* `pytest-pep8 <http://pypi.python.org/pypi/pytest-pep8>`_:
  a ``--pep8`` option to enable PEP8 compliance checking.

* `oejskit <http://pypi.python.org/pypi/oejskit>`_:
  a plugin to run javascript unittests in life browsers

To see a complete list of all plugins with their latest testing
status against different py.test and Python versions, please visit
`pytest-plugs <http://pytest-plugs.herokuapp.com/>`_.

You may also discover more plugins through a `pytest- pypi.python.org search`_.

.. _`available installable plugins`:
.. _`pytest- pypi.python.org search`: http://pypi.python.org/pypi?%3Aaction=search&term=pytest-&submit=search

Writing a plugin by looking at examples
------------------------------------------------------

.. _`Distribute`: http://pypi.python.org/pypi/distribute
.. _`setuptools`: http://pypi.python.org/pypi/setuptools

If you want to write a plugin, there are many real-life examples
you can copy from:

* a custom collection example plugin: :ref:`yaml plugin`
* around 20 `builtin plugins`_ which provide pytest's own functionality
* many `external plugins`_ providing additional features

All of these plugins implement the documented `well specified hooks`_
to extend and add functionality.

.. _`setuptools entry points`:

Making your plugin installable by others
-----------------------------------------------

If you want to make your plugin externally available, you
may define a so-called entry point for your distribution so
that ``pytest`` finds your plugin module.  Entry points are
a feature that is provided by `setuptools`_ or `Distribute`_.
pytest looks up the ``pytest11`` entrypoint to discover its
plugins and you can thus make your plugin available by defining
it in your setuptools/distribute-based setup-invocation:

.. sourcecode:: python

    # sample ./setup.py file
    from setuptools import setup

    setup(
        name="myproject",
        packages = ['myproject']

        # the following makes a plugin available to pytest
        entry_points = {
            'pytest11': [
                'name_of_plugin = myproject.pluginmodule',
            ]
        },
    )

If a package is installed this way, ``pytest`` will load
``myproject.pluginmodule`` as a plugin which can define
`well specified hooks`_.

.. _`pluginorder`:

Plugin discovery order at tool startup
--------------------------------------------

``pytest`` loads plugin modules at tool startup in the following way:

* by loading all builtin plugins

* by loading all plugins registered through `setuptools entry points`_.

* by pre-scanning the command line for the ``-p name`` option
  and loading the specified plugin before actual command line parsing.

* by loading all :file:`conftest.py` files as inferred by the command line
  invocation:

  - if no test paths are specified use current dir as a test path
  - if exists, load ``conftest.py`` and ``test*/conftest.py`` relative 
    to the directory part of the first test path. 

  Note that pytest does not find ``conftest.py`` files in deeper nested
  sub directories at tool startup.  It is usually a good idea to keep
  your conftest.py file in the top level test or project root directory.

* by recursively loading all plugins specified by the
  ``pytest_plugins`` variable in ``conftest.py`` files


Requiring/Loading plugins in a test module or conftest file
-------------------------------------------------------------

You can require plugins in a test module or a conftest file like this::

    pytest_plugins = "name1", "name2",

When the test module or conftest plugin is loaded the specified plugins
will be loaded as well.  You can also use dotted path like this::

    pytest_plugins = "myapp.testsupport.myplugin"

which will import the specified module as a ``pytest`` plugin.


Accessing another plugin by name
--------------------------------------------

If a plugin wants to collaborate with code from
another plugin it can obtain a reference through
the plugin manager like this:

.. sourcecode:: python

    plugin = config.pluginmanager.getplugin("name_of_plugin")

If you want to look at the names of existing plugins, use
the ``--traceconfig`` option.

.. _`findpluginname`:

Finding out which plugins are active
----------------------------------------------------------------------------

If you want to find out which plugins are active in your
environment you can type::

    py.test --traceconfig

and will get an extended test header which shows activated plugins
and their names. It will also print local plugins aka
:ref:`conftest.py <conftest>` files when they are loaded.

.. _`cmdunregister`:

Deactivating / unregistering a plugin by name
----------------------------------------------------------------------------

You can prevent plugins from loading or unregister them::

    py.test -p no:NAME

This means that any subsequent try to activate/load the named
plugin will it already existing.  See :ref:`findpluginname` for
how to obtain the name of a plugin.

.. _`builtin plugins`:

pytest default plugin reference
====================================


You can find the source code for the following plugins
in the `pytest repository <http://bitbucket.org/hpk42/pytest/>`_.

.. autosummary::

    _pytest.assertion
    _pytest.capture
    _pytest.config
    _pytest.doctest
    _pytest.genscript
    _pytest.helpconfig
    _pytest.junitxml
    _pytest.mark
    _pytest.monkeypatch
    _pytest.nose
    _pytest.pastebin
    _pytest.pdb
    _pytest.pytester
    _pytest.python
    _pytest.recwarn
    _pytest.resultlog
    _pytest.runner
    _pytest.main
    _pytest.skipping
    _pytest.terminal
    _pytest.tmpdir
    _pytest.unittest

.. _`well specified hooks`:

pytest hook reference
====================================

Hook specification and validation
-----------------------------------------

``pytest`` calls hook functions to implement initialization, running,
test execution and reporting.  When ``pytest`` loads a plugin it validates
that each hook function conforms to its respective hook specification.
Each hook function name and its argument names need to match a hook
specification.  However, a hook function may accept *fewer* parameters
by simply not specifying them.  If you mistype argument names or the
hook name itself you get an error showing the available arguments.

Initialization, command line and configuration hooks
--------------------------------------------------------------------

.. currentmodule:: _pytest.hookspec

.. autofunction:: pytest_load_initial_conftests
.. autofunction:: pytest_cmdline_preparse
.. autofunction:: pytest_cmdline_parse
.. autofunction:: pytest_namespace
.. autofunction:: pytest_addoption
.. autofunction:: pytest_cmdline_main
.. autofunction:: pytest_configure
.. autofunction:: pytest_unconfigure

Generic "runtest" hooks
------------------------------

All runtest related hooks receive a :py:class:`pytest.Item` object.

.. autofunction:: pytest_runtest_protocol
.. autofunction:: pytest_runtest_setup
.. autofunction:: pytest_runtest_call
.. autofunction:: pytest_runtest_teardown
.. autofunction:: pytest_runtest_makereport

For deeper understanding you may look at the default implementation of
these hooks in :py:mod:`_pytest.runner` and maybe also
in :py:mod:`_pytest.pdb` which interacts with :py:mod:`_pytest.capture`
and its input/output capturing in order to immediately drop
into interactive debugging when a test failure occurs.

The :py:mod:`_pytest.terminal` reported specifically uses
the reporting hook to print information about a test run.

Collection hooks
------------------------------

``pytest`` calls the following hooks for collecting files and directories:

.. autofunction:: pytest_ignore_collect
.. autofunction:: pytest_collect_directory
.. autofunction:: pytest_collect_file

For influencing the collection of objects in Python modules
you can use the following hook:

.. autofunction:: pytest_pycollect_makeitem
.. autofunction:: pytest_generate_tests

After collection is complete, you can modify the order of
items, delete or otherwise amend the test items:

.. autofunction:: pytest_collection_modifyitems

Reporting hooks
------------------------------

Session related reporting hooks:

.. autofunction:: pytest_collectstart
.. autofunction:: pytest_itemcollected
.. autofunction:: pytest_collectreport
.. autofunction:: pytest_deselected

And here is the central hook for reporting about
test execution:

.. autofunction:: pytest_runtest_logreport


Debugging/Interaction hooks
--------------------------------------

There are few hooks which can be used for special
reporting or interaction with exceptions:

.. autofunction:: pytest_internalerror
.. autofunction:: pytest_keyboard_interrupt
.. autofunction:: pytest_exception_interact

Reference of objects involved in hooks
===========================================================

.. autoclass:: _pytest.config.Config()
    :members:

.. autoclass:: _pytest.config.Parser()
    :members:

.. autoclass:: _pytest.main.Node()
    :members:

.. autoclass:: _pytest.main.Collector()
    :members:
    :show-inheritance:

.. autoclass:: _pytest.main.Item()
    :members:
    :show-inheritance:

.. autoclass:: _pytest.python.Module()
    :members:
    :show-inheritance:

.. autoclass:: _pytest.python.Class()
    :members:
    :show-inheritance:

.. autoclass:: _pytest.python.Function()
    :members:
    :show-inheritance:

.. autoclass:: _pytest.runner.CallInfo()
    :members:

.. autoclass:: _pytest.runner.TestReport()
    :members: