pytest / doc / en / example / markers.txt

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.. _`mark examples`:

Working with custom markers
=================================================

Here are some example using the :ref:`mark` mechanism.

Marking test functions and selecting them for a run
----------------------------------------------------

You can "mark" a test function with custom metadata like this::

    # content of test_server.py

    import pytest
    @pytest.mark.webtest
    def test_send_http():
        pass # perform some webtest test for your app
    def test_something_quick():
        pass
    def test_another():
        pass

.. versionadded:: 2.2

You can then restrict a test run to only run tests marked with ``webtest``::

    $ py.test -v -m webtest
    =========================== test session starts ============================
    platform linux2 -- Python 2.7.3 -- pytest-2.3.4.dev3 -- /home/hpk/venv/1/bin/python
    cachedir: /tmp/doc-exec-196/.cache
    plugins: pep8, cache, xdist
    collecting ... collected 3 items
    
    test_server.py:3: test_send_http PASSED
    
    =================== 2 tests deselected by "-m 'webtest'" ===================
    ================== 1 passed, 2 deselected in 0.01 seconds ==================

Or the inverse, running all tests except the webtest ones::
    
    $ py.test -v -m "not webtest"
    =========================== test session starts ============================
    platform linux2 -- Python 2.7.3 -- pytest-2.3.4.dev3 -- /home/hpk/venv/1/bin/python
    cachedir: /tmp/doc-exec-196/.cache
    plugins: pep8, cache, xdist
    collecting ... collected 3 items
    
    test_server.py:6: test_something_quick PASSED
    test_server.py:8: test_another PASSED
    
    ================= 1 tests deselected by "-m 'not webtest'" =================
    ================== 2 passed, 1 deselected in 0.02 seconds ==================

Using ``-k expr`` to select tests based on their name
-------------------------------------------------------

.. versionadded: 2.0/2.3.4

You can use the ``-k`` command line option to specify an expression
which implements a substring match on the test names instead of the
exact match on markers that ``-m`` provides.  This makes it easy to
select tests based on their names::

    $ py.test -v -k http  # running with the above defined example module
    =========================== test session starts ============================
    platform linux2 -- Python 2.7.3 -- pytest-2.3.4.dev3 -- /home/hpk/venv/1/bin/python
    cachedir: /tmp/doc-exec-196/.cache
    plugins: pep8, cache, xdist
    collecting ... collected 3 items
    
    test_server.py:3: test_send_http PASSED
    
    =================== 2 tests deselected by '-ksend_http' ====================
    ================== 1 passed, 2 deselected in 0.01 seconds ==================

And you can also run all tests except the ones that match the keyword::

    $ py.test -k "not send_http" -v
    =========================== test session starts ============================
    platform linux2 -- Python 2.7.3 -- pytest-2.3.4.dev3 -- /home/hpk/venv/1/bin/python
    cachedir: /tmp/doc-exec-196/.cache
    plugins: pep8, cache, xdist
    collecting ... collected 3 items
    
    test_server.py:6: test_something_quick PASSED
    test_server.py:8: test_another PASSED
    
    ================= 1 tests deselected by '-knot send_http' ==================
    ================== 2 passed, 1 deselected in 0.01 seconds ==================

Or to select "http" and "quick" tests::

    $ py.test -k "http or quick" -v
    =========================== test session starts ============================
    platform linux2 -- Python 2.7.3 -- pytest-2.3.4.dev3 -- /home/hpk/venv/1/bin/python
    cachedir: /tmp/doc-exec-196/.cache
    plugins: pep8, cache, xdist
    collecting ... collected 3 items
    
    test_server.py:3: test_send_http PASSED
    test_server.py:6: test_something_quick PASSED
    
    ================= 1 tests deselected by '-khttp or quick' ==================
    ================== 2 passed, 1 deselected in 0.01 seconds ==================

Registering markers
-------------------------------------

.. versionadded:: 2.2

.. ini-syntax for custom markers:

Registering markers for your test suite is simple::

    # content of pytest.ini
    [pytest]
    markers =
        webtest: mark a test as a webtest.

You can ask which markers exist for your test suite - the list includes our just defined ``webtest`` markers::

    $ py.test --markers
    @pytest.mark.webtest: mark a test as a webtest.
    
    @pytest.mark.skipif(condition): skip the given test function if eval(condition) results in a True value.  Evaluation happens within the module global context. Example: skipif('sys.platform == "win32"') skips the test if we are on the win32 platform. see http://pytest.org/latest/skipping.html
    
    @pytest.mark.xfail(condition, reason=None, run=True): mark the the test function as an expected failure if eval(condition) has a True value. Optionally specify a reason for better reporting and run=False if you don't even want to execute the test function. See http://pytest.org/latest/skipping.html
    
    @pytest.mark.parametrize(argnames, argvalues): call a test function multiple times passing in multiple different argument value sets. Example: @parametrize('arg1', [1,2]) would lead to two calls of the decorated test function, one with arg1=1 and another with arg1=2. see http://pytest.org/latest/parametrize.html for more info and examples.
    
    @pytest.mark.usefixtures(fixturename1, fixturename2, ...): mark tests as needing all of the specified fixtures. see http://pytest.org/latest/fixture.html#usefixtures 
    
    @pytest.mark.tryfirst: mark a hook implementation function such that the plugin machinery will try to call it first/as early as possible.
    
    @pytest.mark.trylast: mark a hook implementation function such that the plugin machinery will try to call it last/as late as possible.
    

For an example on how to add and work with markers from a plugin, see
:ref:`adding a custom marker from a plugin`.

.. note::

    It is recommended to explicitely register markers so that:

    * there is one place in your test suite defining your markers

    * asking for existing markers via ``py.test --markers`` gives good output

    * typos in function markers are treated as an error if you use
      the ``--strict`` option. Later versions of py.test are probably
      going to treat non-registered markers as an error.

.. _`scoped-marking`:

Marking whole classes or modules
----------------------------------------------------

If you are programming with Python 2.6 or later you may use ``pytest.mark``
decorators with classes to apply markers to all of its test methods::

    # content of test_mark_classlevel.py
    import pytest
    @pytest.mark.webtest
    class TestClass:
        def test_startup(self):
            pass
        def test_startup_and_more(self):
            pass

This is equivalent to directly applying the decorator to the
two test functions.

To remain backward-compatible with Python 2.4 you can also set a
``pytestmark`` attribute on a TestClass like this::

    import pytest

    class TestClass:
        pytestmark = pytest.mark.webtest

or if you need to use multiple markers you can use a list::

    import pytest

    class TestClass:
        pytestmark = [pytest.mark.webtest, pytest.mark.slowtest]

You can also set a module level marker::

    import pytest
    pytestmark = pytest.mark.webtest

in which case it will be applied to all functions and
methods defined in the module.



.. _`adding a custom marker from a plugin`:

Custom marker and command line option to control test runs
----------------------------------------------------------

.. regendoc:wipe

Plugins can provide custom markers and implement specific behaviour
based on it. This is a self-contained example which adds a command
line option and a parametrized test function marker to run tests
specifies via named environments::

    # content of conftest.py

    import pytest
    def pytest_addoption(parser):
        parser.addoption("-E", action="store", metavar="NAME",
            help="only run tests matching the environment NAME.")

    def pytest_configure(config):
        # register an additional marker
        config.addinivalue_line("markers",
            "env(name): mark test to run only on named environment")

    def pytest_runtest_setup(item):
        envmarker = item.keywords.get("env", None)
        if envmarker is not None:
            envname = envmarker.args[0]
            if envname != item.config.getoption("-E"):
                pytest.skip("test requires env %r" % envname)

A test file using this local plugin::

    # content of test_someenv.py

    import pytest
    @pytest.mark.env("stage1")
    def test_basic_db_operation():
        pass

and an example invocations specifying a different environment than what
the test needs::

    $ py.test -E stage2
    =========================== test session starts ============================
    platform linux2 -- Python 2.7.3 -- pytest-2.3.4.dev3
    plugins: pep8, cache, xdist
    collected 1 items
    
    test_someenv.py s
    
    ======================== 1 skipped in 0.01 seconds =========================
  
and here is one that specifies exactly the environment needed::

    $ py.test -E stage1
    =========================== test session starts ============================
    platform linux2 -- Python 2.7.3 -- pytest-2.3.4.dev3
    plugins: pep8, cache, xdist
    collected 1 items
    
    test_someenv.py .
    
    ========================= 1 passed in 0.01 seconds =========================

The ``--markers`` option always gives you a list of available markers::

    $ py.test --markers
    @pytest.mark.env(name): mark test to run only on named environment
    
    @pytest.mark.skipif(condition): skip the given test function if eval(condition) results in a True value.  Evaluation happens within the module global context. Example: skipif('sys.platform == "win32"') skips the test if we are on the win32 platform. see http://pytest.org/latest/skipping.html
    
    @pytest.mark.xfail(condition, reason=None, run=True): mark the the test function as an expected failure if eval(condition) has a True value. Optionally specify a reason for better reporting and run=False if you don't even want to execute the test function. See http://pytest.org/latest/skipping.html
    
    @pytest.mark.parametrize(argnames, argvalues): call a test function multiple times passing in multiple different argument value sets. Example: @parametrize('arg1', [1,2]) would lead to two calls of the decorated test function, one with arg1=1 and another with arg1=2. see http://pytest.org/latest/parametrize.html for more info and examples.
    
    @pytest.mark.usefixtures(fixturename1, fixturename2, ...): mark tests as needing all of the specified fixtures. see http://pytest.org/latest/fixture.html#usefixtures 
    
    @pytest.mark.tryfirst: mark a hook implementation function such that the plugin machinery will try to call it first/as early as possible.
    
    @pytest.mark.trylast: mark a hook implementation function such that the plugin machinery will try to call it last/as late as possible.
    
    
Reading markers which were set from multiple places
----------------------------------------------------

.. versionadded: 2.2.2

.. regendoc:wipe

If you are heavily using markers in your test suite you may encounter the case where a marker is applied several times to a test function.  From plugin
code you can read over all such settings.  Example::

    # content of test_mark_three_times.py
    import pytest
    pytestmark = pytest.mark.glob("module", x=1)

    @pytest.mark.glob("class", x=2)
    class TestClass:
        @pytest.mark.glob("function", x=3)
        def test_something(self):
            pass

Here we have the marker "glob" applied three times to the same
test function.  From a conftest file we can read it like this::

    # content of conftest.py
    import sys

    def pytest_runtest_setup(item):
        g = item.keywords.get("glob", None)
        if g is not None:
            for info in g:
                print ("glob args=%s kwargs=%s" %(info.args, info.kwargs))
                sys.stdout.flush()

Let's run this without capturing output and see what we get::

    $ py.test -q -s 
    glob args=('function',) kwargs={'x': 3}
    glob args=('class',) kwargs={'x': 2}
    glob args=('module',) kwargs={'x': 1}
    .

marking platform specific tests with pytest
--------------------------------------------------------------

.. regendoc:wipe

Consider you have a test suite which marks tests for particular platforms,
namely ``pytest.mark.osx``, ``pytest.mark.win32`` etc. and you
also have tests that run on all platforms and have no specific
marker.  If you now want to have a way to only run the tests 
for your particular platform, you could use the following plugin::

    # content of conftest.py
    #
    import sys
    import pytest

    ALL = set("osx linux2 win32".split())

    def pytest_runtest_setup(item):
        if isinstance(item, item.Function):
            plat = sys.platform
            if plat not in item.keywords:
                if ALL.intersection(item.keywords):
                    pytest.skip("cannot run on platform %s" %(plat))

then tests will be skipped if they were specified for a different platform.
Let's do a little test file to show how this looks like::

    # content of test_plat.py

    import pytest

    @pytest.mark.osx
    def test_if_apple_is_evil():
        pass

    @pytest.mark.linux2
    def test_if_linux_works():
        pass

    @pytest.mark.win32
    def test_if_win32_crashes():
        pass

    def test_runs_everywhere():
        pass

then you will see two test skipped and two executed tests as expected::

    $ py.test -rs # this option reports skip reasons
    =========================== test session starts ============================
    platform linux2 -- Python 2.7.3 -- pytest-2.3.4.dev3
    plugins: pep8, cache, xdist
    collected 4 items
    
    test_plat.py s.s.
    ========================= short test summary info ==========================
    SKIP [2] /tmp/doc-exec-196/conftest.py:12: cannot run on platform linux2
    
    =================== 2 passed, 2 skipped in 0.02 seconds ====================

Note that if you specify a platform via the marker-command line option like this::

    $ py.test -m linux2
    =========================== test session starts ============================
    platform linux2 -- Python 2.7.3 -- pytest-2.3.4.dev3
    plugins: pep8, cache, xdist
    collected 4 items
    
    test_plat.py .
    
    =================== 3 tests deselected by "-m 'linux2'" ====================
    ================== 1 passed, 3 deselected in 0.02 seconds ==================

then the unmarked-tests will not be run.  It is thus a way to restrict the run to the specific tests.   

Automatically adding markers based on test names
--------------------------------------------------------

.. regendoc:wipe

If you a test suite where test function names indicate a certain
type of test, you can implement a hook that automatically defines
markers so that you can use the ``-m`` option with it. Let's look
at this test module::

    # content of test_module.py

    def test_interface_simple():
        assert 0

    def test_interface_complex():
        assert 0
    
    def test_event_simple():
        assert 0

    def test_something_else():
        assert 0

We want to dynamically define two markers and can do it in a
``conftest.py`` plugin::

    # content of conftest.py
    
    import pytest
    def pytest_collection_modifyitems(items):
        for item in items:
            if "interface" in item.nodeid:
                item.keywords["interface"] = pytest.mark.interface
            elif "event" in item.nodeid:
                item.keywords["event"] = pytest.mark.event

We can now use the ``-m option`` to select one set::

  $ py.test -m interface --tb=short
  =========================== test session starts ============================
  platform linux2 -- Python 2.7.3 -- pytest-2.3.4.dev3
  plugins: pep8, cache, xdist
  collected 4 items
  
  test_module.py FF
  
  ================================= FAILURES =================================
  __________________________ test_interface_simple ___________________________
  test_module.py:3: in test_interface_simple
  >       assert 0
  E       assert 0
  __________________________ test_interface_complex __________________________
  test_module.py:6: in test_interface_complex
  >       assert 0
  E       assert 0
  ================== 2 tests deselected by "-m 'interface'" ==================
  ================== 2 failed, 2 deselected in 0.02 seconds ==================

or to select both "event" and "interface" tests::

  $ py.test -m "interface or event" --tb=short
  =========================== test session starts ============================
  platform linux2 -- Python 2.7.3 -- pytest-2.3.4.dev3
  plugins: pep8, cache, xdist
  collected 4 items
  
  test_module.py FFF
  
  ================================= FAILURES =================================
  __________________________ test_interface_simple ___________________________
  test_module.py:3: in test_interface_simple
  >       assert 0
  E       assert 0
  __________________________ test_interface_complex __________________________
  test_module.py:6: in test_interface_complex
  >       assert 0
  E       assert 0
  ____________________________ test_event_simple _____________________________
  test_module.py:9: in test_event_simple
  >       assert 0
  E       assert 0
  ============= 1 tests deselected by "-m 'interface or event'" ==============
  ================== 3 failed, 1 deselected in 0.02 seconds ==================
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