576 lines
18 KiB
ReStructuredText
576 lines
18 KiB
ReStructuredText
.. _plugins:
|
|
.. _`writing-plugins`:
|
|
|
|
Writing plugins
|
|
===============
|
|
|
|
It is easy to implement `local conftest plugins`_ for your own project
|
|
or `pip-installable plugins`_ that can be used throughout many projects,
|
|
including third party projects. Please refer to :ref:`using plugins` if you
|
|
only want to use but not write plugins.
|
|
|
|
A plugin contains one or multiple hook functions. :ref:`Writing hooks <writinghooks>`
|
|
explains the basics and details of how you can write a hook function yourself.
|
|
``pytest`` implements all aspects of configuration, collection, running and
|
|
reporting by calling `well specified hooks`_ of the following plugins:
|
|
|
|
* :ref:`builtin plugins`: loaded from pytest's internal ``_pytest`` directory.
|
|
|
|
* :ref:`external plugins <extplugins>`: modules discovered through
|
|
`setuptools entry points`_
|
|
|
|
* `conftest.py plugins`_: modules auto-discovered in test directories
|
|
|
|
In principle, each hook call is a ``1:N`` Python function call where ``N`` is the
|
|
number of registered implementation functions for a given specification.
|
|
All specifications and implementations following the ``pytest_`` prefix
|
|
naming convention, making them easy to distinguish and find.
|
|
|
|
.. _`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
|
|
|
|
|
|
.. _`pytest/plugin`: http://bitbucket.org/pytest-dev/pytest/src/tip/pytest/plugin/
|
|
.. _`conftest.py plugins`:
|
|
.. _`conftest.py`:
|
|
.. _`localplugin`:
|
|
.. _`conftest`:
|
|
.. _`local conftest plugins`:
|
|
|
|
conftest.py: local per-directory plugins
|
|
----------------------------------------
|
|
|
|
Local ``conftest.py`` plugins contain directory-specific hook
|
|
implementations. Hook Session and test running activities will
|
|
invoke all hooks defined in ``conftest.py`` files closer to the
|
|
root of the filesystem. Example of implementing the
|
|
``pytest_runtest_setup`` hook so that is called for tests in the ``a``
|
|
sub directory but not for other directories::
|
|
|
|
a/conftest.py:
|
|
def pytest_runtest_setup(item):
|
|
# called for running each test in 'a' directory
|
|
print ("setting up", item)
|
|
|
|
a/test_sub.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 practice for projects to either put ``conftest.py``
|
|
under a package scope or to never import anything from a
|
|
conftest.py file.
|
|
|
|
|
|
Writing your own plugin
|
|
-----------------------
|
|
|
|
.. _`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 :ref:`builtin plugins` which provide pytest's own functionality
|
|
* many `external plugins <http://plugincompat.herokuapp.com>`_ providing additional features
|
|
|
|
All of these plugins implement the documented `well specified hooks`_
|
|
to extend and add functionality.
|
|
|
|
.. note::
|
|
Make sure to check out the excellent
|
|
`cookiecutter-pytest-plugin <https://github.com/pytest-dev/cookiecutter-pytest-plugin>`_
|
|
project, which is a `cookiecutter template <https://github.com/audreyr/cookiecutter>`_
|
|
for authoring plugins.
|
|
|
|
The template provides an excellent starting point with a working plugin,
|
|
tests running with tox, comprehensive README and
|
|
entry-pointy already pre-configured.
|
|
|
|
Also consider :ref:`contributing your plugin to pytest-dev<submitplugin>`
|
|
once it has some happy users other than yourself.
|
|
|
|
|
|
.. _`setuptools entry points`:
|
|
.. _`pip-installable plugins`:
|
|
|
|
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`_. pytest looks up
|
|
the ``pytest11`` entrypoint to discover its
|
|
plugins and you can thus make your plugin available by defining
|
|
it in your setuptools-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`_.
|
|
|
|
|
|
|
|
|
|
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.
|
|
|
|
Testing plugins
|
|
---------------
|
|
|
|
pytest comes with some facilities that you can enable for testing your
|
|
plugin. Given that you have an installed plugin you can enable the
|
|
:py:class:`testdir <_pytest.pytester.Testdir>` fixture via specifying a
|
|
command line option to include the pytester plugin (``-p pytester``) or
|
|
by putting ``pytest_plugins = "pytester"`` into your test or
|
|
``conftest.py`` file. You then will have a ``testdir`` fixture which you
|
|
can use like this::
|
|
|
|
# content of test_myplugin.py
|
|
|
|
pytest_plugins = "pytester" # to get testdir fixture
|
|
|
|
def test_myplugin(testdir):
|
|
testdir.makepyfile("""
|
|
def test_example():
|
|
pass
|
|
""")
|
|
result = testdir.runpytest("--verbose")
|
|
result.fnmatch_lines("""
|
|
test_example*
|
|
""")
|
|
|
|
Note that by default ``testdir.runpytest()`` will perform a pytest
|
|
in-process. You can pass the command line option ``--runpytest=subprocess``
|
|
to have it happen in a subprocess.
|
|
|
|
Also see the :py:class:`RunResult <_pytest.pytester.RunResult>` for more
|
|
methods of the result object that you get from a call to ``runpytest``.
|
|
|
|
.. _`writinghooks`:
|
|
|
|
Writing hook functions
|
|
======================
|
|
|
|
|
|
.. _validation:
|
|
|
|
hook function validation and execution
|
|
--------------------------------------
|
|
|
|
pytest calls hook functions from registered plugins for any
|
|
given hook specification. Let's look at a typical hook function
|
|
for the ``pytest_collection_modifyitems(session, config,
|
|
items)`` hook which pytest calls after collection of all test items is
|
|
completed.
|
|
|
|
When we implement a ``pytest_collection_modifyitems`` function in our plugin
|
|
pytest will during registration verify that you use argument
|
|
names which match the specification and bail out if not.
|
|
|
|
Let's look at a possible implementation:
|
|
|
|
.. code-block:: python
|
|
|
|
def pytest_collection_modifyitems(config, items):
|
|
# called after collection is completed
|
|
# you can modify the ``items`` list
|
|
|
|
Here, ``pytest`` will pass in ``config`` (the pytest config object)
|
|
and ``items`` (the list of collected test items) but will not pass
|
|
in the ``session`` argument because we didn't list it in the function
|
|
signature. This dynamic "pruning" of arguments allows ``pytest`` to
|
|
be "future-compatible": we can introduce new hook named parameters without
|
|
breaking the signatures of existing hook implementations. It is one of
|
|
the reasons for the general long-lived compatibility of pytest plugins.
|
|
|
|
Note that hook functions other than ``pytest_runtest_*`` are not
|
|
allowed to raise exceptions. Doing so will break the pytest run.
|
|
|
|
|
|
|
|
firstresult: stop at first non-None result
|
|
-------------------------------------------
|
|
|
|
Most calls to ``pytest`` hooks result in a **list of results** which contains
|
|
all non-None results of the called hook functions.
|
|
|
|
Some hook specifications use the ``firstresult=True`` option so that the hook
|
|
call only executes until the first of N registered functions returns a
|
|
non-None result which is then taken as result of the overall hook call.
|
|
The remaining hook functions will not be called in this case.
|
|
|
|
|
|
hookwrapper: executing around other hooks
|
|
-------------------------------------------------
|
|
|
|
.. currentmodule:: _pytest.core
|
|
|
|
.. versionadded:: 2.7 (experimental)
|
|
|
|
pytest plugins can implement hook wrappers which wrap the execution
|
|
of other hook implementations. A hook wrapper is a generator function
|
|
which yields exactly once. When pytest invokes hooks it first executes
|
|
hook wrappers and passes the same arguments as to the regular hooks.
|
|
|
|
At the yield point of the hook wrapper pytest will execute the next hook
|
|
implementations and return their result to the yield point in the form of
|
|
a :py:class:`CallOutcome` instance which encapsulates a result or
|
|
exception info. The yield point itself will thus typically not raise
|
|
exceptions (unless there are bugs).
|
|
|
|
Here is an example definition of a hook wrapper::
|
|
|
|
import pytest
|
|
|
|
@pytest.hookimpl(hookwrapper=True)
|
|
def pytest_pyfunc_call(pyfuncitem):
|
|
# do whatever you want before the next hook executes
|
|
|
|
outcome = yield
|
|
# outcome.excinfo may be None or a (cls, val, tb) tuple
|
|
|
|
res = outcome.get_result() # will raise if outcome was exception
|
|
# postprocess result
|
|
|
|
Note that hook wrappers don't return results themselves, they merely
|
|
perform tracing or other side effects around the actual hook implementations.
|
|
If the result of the underlying hook is a mutable object, they may modify
|
|
that result but it's probably better to avoid it.
|
|
|
|
|
|
Hook function ordering / call example
|
|
-------------------------------------
|
|
|
|
For any given hook specification there may be more than one
|
|
implementation and we thus generally view ``hook`` execution as a
|
|
``1:N`` function call where ``N`` is the number of registered functions.
|
|
There are ways to influence if a hook implementation comes before or
|
|
after others, i.e. the position in the ``N``-sized list of functions:
|
|
|
|
.. code-block:: python
|
|
|
|
# Plugin 1
|
|
@pytest.hookimpl(tryfirst=True)
|
|
def pytest_collection_modifyitems(items):
|
|
# will execute as early as possible
|
|
|
|
# Plugin 2
|
|
@pytest.hookimpl(trylast=True)
|
|
def pytest_collection_modifyitems(items):
|
|
# will execute as late as possible
|
|
|
|
# Plugin 3
|
|
@pytest.hookimpl(hookwrapper=True)
|
|
def pytest_collection_modifyitems(items):
|
|
# will execute even before the tryfirst one above!
|
|
outcome = yield
|
|
# will execute after all non-hookwrappers executed
|
|
|
|
Here is the order of execution:
|
|
|
|
1. Plugin3's pytest_collection_modifyitems called until the yield point
|
|
because it is a hook wrapper.
|
|
|
|
2. Plugin1's pytest_collection_modifyitems is called because it is marked
|
|
with ``tryfirst=True``.
|
|
|
|
3. Plugin2's pytest_collection_modifyitems is called because it is marked
|
|
with ``trylast=True`` (but even without this mark it would come after
|
|
Plugin1).
|
|
|
|
4. Plugin3's pytest_collection_modifyitems then executing the code after the yield
|
|
point. The yield receives a :py:class:`CallOutcome` instance which encapsulates
|
|
the result from calling the non-wrappers. Wrappers shall not modify the result.
|
|
|
|
It's possible to use ``tryfirst`` and ``trylast`` also in conjunction with
|
|
``hookwrapper=True`` in which case it will influence the ordering of hookwrappers
|
|
among each other.
|
|
|
|
|
|
Declaring new hooks
|
|
------------------------
|
|
|
|
.. currentmodule:: _pytest.hookspec
|
|
|
|
Plugins and ``conftest.py`` files may declare new hooks that can then be
|
|
implemented by other plugins in order to alter behaviour or interact with
|
|
the new plugin:
|
|
|
|
.. autofunction:: pytest_addhooks
|
|
|
|
Hooks are usually declared as do-nothing functions that contain only
|
|
documentation describing when the hook will be called and what return values
|
|
are expected.
|
|
|
|
For an example, see `newhooks.py`_ from :ref:`xdist`.
|
|
|
|
.. _`newhooks.py`: https://github.com/pytest-dev/pytest-xdist/blob/974bd566c599dc6a9ea291838c6f226197208b46/xdist/newhooks.py
|
|
|
|
|
|
Optionally using hooks from 3rd party plugins
|
|
---------------------------------------------
|
|
|
|
Using new hooks from plugins as explained above might be a little tricky
|
|
because of the standard :ref:`validation mechanism <validation>`:
|
|
if you depend on a plugin that is not installed, validation will fail and
|
|
the error message will not make much sense to your users.
|
|
|
|
One approach is to defer the hook implementation to a new plugin instead of
|
|
declaring the hook functions directly in your plugin module, for example::
|
|
|
|
# contents of myplugin.py
|
|
|
|
class DeferPlugin(object):
|
|
"""Simple plugin to defer pytest-xdist hook functions."""
|
|
|
|
def pytest_testnodedown(self, node, error):
|
|
"""standard xdist hook function.
|
|
"""
|
|
|
|
def pytest_configure(config):
|
|
if config.pluginmanager.hasplugin('xdist'):
|
|
config.pluginmanager.register(DeferPlugin())
|
|
|
|
This has the added benefit of allowing you to conditionally install hooks
|
|
depending on which plugins are installed.
|
|
|
|
.. _`well specified hooks`:
|
|
|
|
.. currentmodule:: _pytest.hookspec
|
|
|
|
pytest hook reference
|
|
=====================
|
|
|
|
|
|
Initialization, command line and configuration hooks
|
|
----------------------------------------------------
|
|
|
|
.. 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
|
|
.. autofunction:: pytest_report_header
|
|
.. autofunction:: pytest_report_teststatus
|
|
.. autofunction:: pytest_terminal_summary
|
|
|
|
And here is the central hook for reporting about
|
|
test execution:
|
|
|
|
.. autofunction:: pytest_runtest_logreport
|
|
|
|
You can also use this hook to customize assertion representation for some
|
|
types:
|
|
|
|
.. autofunction:: pytest_assertrepr_compare
|
|
|
|
|
|
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
|
|
.. autofunction:: pytest_enter_pdb
|
|
|
|
|
|
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:
|
|
|
|
.. autoclass:: _pytest.vendored_packages.pluggy._CallOutcome()
|
|
:members:
|
|
|
|
.. autofunction:: _pytest.config.get_plugin_manager()
|
|
|
|
.. autoclass:: _pytest.config.PytestPluginManager()
|
|
:members:
|
|
:undoc-members:
|
|
:show-inheritance:
|
|
|
|
.. autoclass:: pluggy.PluginManager()
|
|
:members:
|
|
|
|
.. currentmodule:: _pytest.pytester
|
|
|
|
.. autoclass:: Testdir()
|
|
:members: runpytest,runpytest_subprocess,runpytest_inprocess,makeconftest,makepyfile
|
|
|
|
.. autoclass:: RunResult()
|
|
:members:
|
|
|
|
.. autoclass:: LineMatcher()
|
|
:members:
|