422 lines
14 KiB
Plaintext
422 lines
14 KiB
Plaintext
================================================
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Customizing and Extending py.test
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================================================
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.. contents::
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:local:
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:depth: 2
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basic test configuration
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===================================
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available command line options
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---------------------------------
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You can see command line options by running::
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py.test -h
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This will display all available command line options
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in your specific environment.
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.. _`project-specific test configuration`:
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.. _`collect_ignore`:
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conftest.py: project specific hooks and configuration
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--------------------------------------------------------
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A unique feature of py.test are its ``conftest.py`` files which
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allow to:
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* `set option defaults`_
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* `implement hooks`_
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* `specify funcargs`_
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or set particular variables to influence the testing process:
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* ``pytest_plugins``: list of named plugins to load
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* ``collect_ignore``: list of paths to ignore during test collection, relative to the containing ``conftest.py`` file
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* ``rsyncdirs``: list of to-be-rsynced directories for distributed
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testing, relative to the containing ``conftest.py`` file.
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You may put a conftest.py files in your project root directory or into
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your package directory if you want to add project-specific test options.
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``py.test`` loads all ``conftest.py`` files upwards from the command
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line file arguments. It usually looks up configuration values
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right-to-left, i.e. the closer conftest files will be checked first.
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This means you can have a ``conftest.py`` in your very home directory to
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have some global configuration values.
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.. _`specify funcargs`: funcargs.html#application-setup-tutorial-example
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.. _`set option defaults`:
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setting persistent option defaults
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------------------------------------
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py.test will lookup option values in this order:
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* command line
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* conftest.py files
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* environment variables
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To find out about the particular switches and type::
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py.test --help-config
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This will print information about all options in your
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environment, including your local plugins.
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.. _`basetemp`:
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Temporary directories
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-------------------------------------------
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You can create directories by calling one of two methods
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on the config object:
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- ``config.mktemp(basename)``: create and return a new tempdir
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- ``config.ensuretemp(basename)``: create or return a new tempdir
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temporary directories are created as sub directories of a per-session
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testdir and will keep around the directories of the last three test
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runs. You can set the base temporary directory through the command line
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`--basetemp`` option. When distributing tests on the same machine,
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``py.test`` takes care to configure a basetemp directory for the sub
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processes such that all temporary data lands below below a single
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per-test run basetemp directory.
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.. _`function arguments`: funcargs.html
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.. _`extensions`:
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Plugin basics
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=========================
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.. _`local plugin`:
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project specific "local" or named "global" plugins
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--------------------------------------------------------------
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py.test implements much of its functionality by calling `well specified
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hooks`_. Python modules which contain such hook functions are called
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plugins. Hook functions are discovered in ``conftest.py`` files or in
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`named plugins`_. ``conftest.py`` files are sometimes called
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"anonymous" or conftest plugins. They are useful for keeping test
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extensions close to your application. Named plugins are normal python
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modules or packages that can be distributed separately. Named plugins
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need to follow a naming pattern; they have an all lowercase ``pytest_``
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prefixed name. While conftest plugins are discovered automatically,
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named plugins must be explicitely specified.
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.. _`named plugins`: plugin/index.html
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.. _`tool startup`:
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.. _`loaded at tool startup`:
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.. _`test tool starts up`:
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Plugin discovery at tool startup
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--------------------------------------------
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py.test loads plugin modules at tool startup in the following way:
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* by reading the ``PYTEST_PLUGINS`` environment variable
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and importing the comma-separated list of named plugins.
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* by pre-scanning the command line for the ``-p name`` option
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and loading the specified plugin before actual command line parsing.
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* by loading all `conftest.py plugin`_ files as inferred by the command line
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invocation
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* by recursively loading all plugins specified by the
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``pytest_plugins`` variable in a ``conftest.py`` file
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Note that at tool startup only ``conftest.py`` files in
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the directory of the specified test modules (or the current dir if None)
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or any of the parent directories are found. There is no try to
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pre-scan all subdirectories to find ``conftest.py`` files or test
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modules.
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Specifying plugins in a test module or plugin
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-----------------------------------------------
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You can specify plugins in a test module or a plugin like this:
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.. sourcecode:: python
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pytest_plugins = "name1", "name2",
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When the test module or plugin is loaded the specified plugins
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will be loaded. If you specify plugins without the ``pytest_``
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prefix it will be automatically added. All plugin names
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must be lowercase.
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.. _`conftest.py plugin`:
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.. _`conftestplugin`:
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conftest.py as anonymous per-project plugins
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--------------------------------------------------
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The purpose of ``conftest.py`` files is to allow `project-specific
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test configuration`_. They thus make for a good place to implement
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project-specific test related features through hooks. For example you may
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set the `collect_ignore`_ variable depending on a command line option
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by defining the following hook in a ``conftest.py`` file:
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.. _`exclude-file-example`:
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.. sourcecode:: python
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# ./conftest.py in your root or package dir
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collect_ignore = ['hello', 'test_world.py']
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def pytest_addoption(parser):
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parser.addoption("--runall", action="store_true", default=False)
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def pytest_configure(config):
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if config.getvalue("runall"):
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collect_ignore[:] = []
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.. _`well specified hooks`:
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.. _`implement hooks`:
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Important py.test hooks
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====================================
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py.test calls hooks functions to implement its `test collection`_,
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running and reporting process. When py.test loads a plugin it validates
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that all hook functions conform to the `hook definition specification`_.
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The hook function name and its
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argument names need to match exactly but it is allowed for an implementation
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to accept *less* parameters. You'll get useful errors on mistyped hook or
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argument names. Read on for some introductory information on particular
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hooks. It's sensible to look at existing plugins so see example usages
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and start off with your own plugin.
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.. _`hook definition specification`: plugin/hookspec.html
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.. _`configuration hooks`:
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command line parsing and configuration hooks
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--------------------------------------------------------------------
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When the `test tool starts up`_ it will invoke all hooks that add
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command line options in the python standard optparse style.
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.. sourcecode:: python
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def pytest_addoption(parser):
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""" add command line options. """"
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parser.addoption("--myopt", dest="myopt", action="store_true")
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After all these hooks have been called, the command line is parser
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and a ``config`` object is created and another hook is invoked,
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for example:
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.. sourcecode:: python
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def pytest_configure(config):
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config.getvalue("myopt")
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When the test run finishes this corresponding finalizer hook is called:
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def pytest_unconfigure(config):
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...
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adding global py.test helpers and functionality
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--------------------------------------------------------------------
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If you want to make global helper functions or objects available
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to your test code you can implement:
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def pytest_namespace():
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""" return dictionary with items to be made available on py.test. namespace """
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All such returned items will be made available directly on
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the ``py.test`` namespace.
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If you want to provide helpers that are specific to a test function run or need
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to be setup per test function run, please refer to the `funcargs mechanism`_.
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.. _`funcargs mechanism`: funcargs.html
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generic "runtest" hooks
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------------------------------
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Each test item is usually executed by calling the following three hooks:
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.. sourcecode:: python
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pytest_runtest_setup(item)
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pytest_runtest_call(item)
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pytest_runtest_teardown(item)
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For each of the three invocations a `call object`_ encapsulates
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information about the outcome of the call and is subsequently used
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to make a report object:
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.. sourcecode:: python
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report = hook.pytest_runtest_makereport(item, call)
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For example, the `pytest_pdb plugin`_ uses this hook to activate
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interactive debugging on failures when ``--pdb`` is specified on the
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command line.
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Usually three reports will be generated for a single test item for each
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of the three runtest hooks respectively. If ``pytest_runtest_setup``
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fails then ``pytest_runtest_teardown`` will be called but not
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``pytest_runtest_call``.
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Each of the up to three reports is eventually fed to the logreport hook:
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.. sourcecode:: python
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pytest_runtest_logreport(report)
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A ``report`` object contains status and reporting information:
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.. sourcecode:: python
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report.longrepr = string/lines/object to print
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report.when = "setup", "call" or "teardown"
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report.shortrepr = letter for progress-report
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report.passed = True or False
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report.failed = True or False
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report.skipped = True or False
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The `pytest_terminal plugin`_ uses this hook to print information
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about a test run.
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The whole protocol described here is implemented via this hook:
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.. sourcecode:: python
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pytest_runtest_protocol(item) -> True
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.. _`call object`:
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The call object contains information about a performed call:
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.. sourcecode:: python
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call.excinfo = ExceptionInfo object or None
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call.when = "setup", "call" or "teardown"
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call.outerr = None or tuple of strings representing captured stdout/stderr
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.. _`pytest_pdb plugin`: http://bitbucket.org/hpk42/py-trunk/src/tip/py/test/plugin/pytest_pdb.py
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.. _`pytest_terminal plugin`: http://bitbucket.org/hpk42/py-trunk/src/tip/py/test/plugin/pytest_terminal.py
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generic collection hooks
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------------------------------
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py.test calls the following two fundamental hooks for collecting files and directories:
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.. sourcecode:: python
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def pytest_collect_directory(path, parent):
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""" return Collection node or None for the given path. """
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def pytest_collect_file(path, parent):
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""" return Collection node or None for the given path. """
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Both return a `collection node`_ for a given path. All returned
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nodes from all hook implementations will participate in the
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collection and running protocol. The ``parent`` object is
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the parent node and may be used to access command line
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options via the ``parent.config`` object.
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Python test function and module hooks
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----------------------------------------------------
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For influencing the collection of objects in Python modules
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you can use the following hook:
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.. sourcecode:: python
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def pytest_pycollect_makeitem(collector, name, obj):
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""" return custom item/collector for a python object in a module, or None. """
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This hook will be called for each Python object in a collected
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Python module. The return value is a custom `collection node`_ or None.
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.. XXX or ``False`` if you want to indicate that the given item should not be collected.
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.. _`collection process`:
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.. _`collection node`:
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.. _`test collection`:
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Test Collection process
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======================================================
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the collection tree
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---------------------------------
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The collecting process is iterative so that distribution
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and execution of tests can start as soon as the first test
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item is collected. Collection nodes with children are
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called "Collectors" and terminal nodes are called "Items".
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Here is an example of such a tree, generated with the
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command ``py.test --collectonly py/xmlobj``::
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<Directory 'xmlobj'>
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<Directory 'testing'>
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<Module 'test_html.py' (py.__.xmlobj.testing.test_html)>
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<Function 'test_html_name_stickyness'>
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<Function 'test_stylenames'>
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<Function 'test_class_None'>
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<Function 'test_alternating_style'>
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<Module 'test_xml.py' (py.__.xmlobj.testing.test_xml)>
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<Function 'test_tag_with_text'>
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<Function 'test_class_identity'>
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<Function 'test_tag_with_text_and_attributes'>
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<Function 'test_tag_with_subclassed_attr_simple'>
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<Function 'test_tag_nested'>
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<Function 'test_tag_xmlname'>
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By default all directories not starting with a dot are traversed,
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looking for ``test_*.py`` and ``*_test.py`` files. Those Python
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files are imported under their `package name`_.
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The Module collector looks for test functions
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and test classes and methods. Test functions and methods
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are prefixed ``test`` by default. Test classes must
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start with a capitalized ``Test`` prefix.
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.. _`package name`:
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constructing the package name for test modules
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-------------------------------------------------
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Test modules are imported under their fully qualified
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name. Given a filesystem ``fspath`` it is constructed as follows:
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* walk the directories up to the last one that contains
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an ``__init__.py`` file.
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* perform ``sys.path.insert(0, basedir)``.
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* import the root package as ``root``
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* determine the fully qualified name for ``fspath`` by either:
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* calling ``root.__pkg__.getimportname(fspath)`` if the
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``__pkg__`` exists.` or
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* otherwise use the relative path of the module path to
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the base dir and turn slashes into dots and strike
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the trailing ``.py``.
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