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Add docs for the warnings functionality

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Bruno Oliveira 2017-03-20 23:35:01 -03:00
parent fa56114115
commit eabe3eed6b
4 changed files with 241 additions and 142 deletions
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2
doc/en/contents.rst
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@ -18,7 +18,7 @@ Full pytest documentation
monkeypatch
tmpdir
capture
recwarn
warnings
doctest
mark
skipping

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doc/en/customize.rst
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@ -240,3 +240,23 @@ Builtin configuration file options
By default, pytest will stop searching for ``conftest.py`` files upwards
from ``pytest.ini``/``tox.ini``/``setup.cfg`` of the project if any,
or up to the file-system root.
.. confval:: filterwarnings
.. versionadded:: 3.1
Sets a list of filters and actions that should be taken for matched
warnings. By default all warnings emitted during the test session
will be displayed in a summary at the end of the test session.
.. code-block:: ini
# content of pytest.ini
[pytest]
filterwarnings =
error
ignore::DeprecationWarning
This tells pytest to ignore deprecation warnings and turn all other warnings
into errors. For more information please refer to :ref:`warnings`.

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@ -1,142 +1,3 @@
.. _`asserting warnings`:
:orphan:
.. _assertwarnings:
Asserting Warnings
=====================================================
.. _`asserting warnings with the warns function`:
.. _warns:
Asserting warnings with the warns function
-----------------------------------------------
.. versionadded:: 2.8
You can check that code raises a particular warning using ``pytest.warns``,
which works in a similar manner to :ref:`raises <assertraises>`::
import warnings
import pytest
def test_warning():
with pytest.warns(UserWarning):
warnings.warn("my warning", UserWarning)
The test will fail if the warning in question is not raised.
You can also call ``pytest.warns`` on a function or code string::
pytest.warns(expected_warning, func, *args, **kwargs)
pytest.warns(expected_warning, "func(*args, **kwargs)")
The function also returns a list of all raised warnings (as
``warnings.WarningMessage`` objects), which you can query for
additional information::
with pytest.warns(RuntimeWarning) as record:
warnings.warn("another warning", RuntimeWarning)
# check that only one warning was raised
assert len(record) == 1
# check that the message matches
assert record[0].message.args[0] == "another warning"
Alternatively, you can examine raised warnings in detail using the
:ref:`recwarn <recwarn>` fixture (see below).
.. note::
``DeprecationWarning`` and ``PendingDeprecationWarning`` are treated
differently; see :ref:`ensuring_function_triggers`.
.. _`recording warnings`:
.. _recwarn:
Recording warnings
------------------------
You can record raised warnings either using ``pytest.warns`` or with
the ``recwarn`` fixture.
To record with ``pytest.warns`` without asserting anything about the warnings,
pass ``None`` as the expected warning type::
with pytest.warns(None) as record:
warnings.warn("user", UserWarning)
warnings.warn("runtime", RuntimeWarning)
assert len(record) == 2
assert str(record[0].message) == "user"
assert str(record[1].message) == "runtime"
The ``recwarn`` fixture will record warnings for the whole function::
import warnings
def test_hello(recwarn):
warnings.warn("hello", UserWarning)
assert len(recwarn) == 1
w = recwarn.pop(UserWarning)
assert issubclass(w.category, UserWarning)
assert str(w.message) == "hello"
assert w.filename
assert w.lineno
Both ``recwarn`` and ``pytest.warns`` return the same interface for recorded
warnings: a WarningsRecorder instance. To view the recorded warnings, you can
iterate over this instance, call ``len`` on it to get the number of recorded
warnings, or index into it to get a particular recorded warning. It also
provides these methods:
.. autoclass:: _pytest.recwarn.WarningsRecorder()
:members:
Each recorded warning has the attributes ``message``, ``category``,
``filename``, ``lineno``, ``file``, and ``line``. The ``category`` is the
class of the warning. The ``message`` is the warning itself; calling
``str(message)`` will return the actual message of the warning.
.. note::
:class:`RecordedWarning` was changed from a plain class to a namedtuple in pytest 3.1
.. note::
``DeprecationWarning`` and ``PendingDeprecationWarning`` are treated
differently; see :ref:`ensuring_function_triggers`.
.. _`ensuring a function triggers a deprecation warning`:
.. _ensuring_function_triggers:
Ensuring a function triggers a deprecation warning
-------------------------------------------------------
You can also call a global helper for checking
that a certain function call triggers a ``DeprecationWarning`` or
``PendingDeprecationWarning``::
import pytest
def test_global():
pytest.deprecated_call(myfunction, 17)
By default, ``DeprecationWarning`` and ``PendingDeprecationWarning`` will not be
caught when using ``pytest.warns`` or ``recwarn`` because default Python warnings filters hide
them. If you wish to record them in your own code, use the
command ``warnings.simplefilter('always')``::
import warnings
import pytest
def test_deprecation(recwarn):
warnings.simplefilter('always')
warnings.warn("deprecated", DeprecationWarning)
assert len(recwarn) == 1
assert recwarn.pop(DeprecationWarning)
You can also use it as a contextmanager::
def test_global():
with pytest.deprecated_call():
myobject.deprecated_method()
This page has been moved, please see :ref:`assertwarnings`.

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@ -0,0 +1,218 @@
.. _`warnings`:
Warnings Capture
================
.. versionadded:: 3.1
Starting from version ``3.1``, pytest now automatically catches all warnings during test execution
and displays them at the end of the session::
# content of test_show_warnings.py
import warnings
def deprecated_function():
warnings.warn("this function is deprecated, use another_function()", DeprecationWarning)
return 1
def test_one():
assert deprecated_function() == 1
Running pytest now produces this output::
$ pytest test_show_warnings.py
.
============================== warnings summary ===============================
test_show_warning.py::test_one
C:\pytest\.tmp\test_show_warning.py:4: DeprecationWarning: this function is deprecated, use another_function()
warnings.warn("this function is deprecated, use another_function()", DeprecationWarning)
-- Docs: http://doc.pytest.org/en/latest/warnings.html
1 passed, 1 warnings in 0.01 seconds
The ``-W`` flag can be passed to control which warnings will be displayed or even turn
them into errors::
$ pytest -q test_show_warning.py -W error::DeprecationWarning
F
================================== FAILURES ===================================
__________________________________ test_one ___________________________________
def test_one():
> assert deprecated_function() == 1
test_show_warning.py:8:
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
def deprecated_function():
> warnings.warn("this function is deprecated, use another_function()", DeprecationWarning)
E DeprecationWarning: this function is deprecated, use another_function()
test_show_warning.py:4: DeprecationWarning
1 failed in 0.02 seconds
The same option can be set in the ``pytest.ini`` file using the ``filterwarnings`` ini option.
For example, the configuration below will ignore all deprecation warnings, but will transform
all other warnings into errors.
.. code-block:: ini
[pytest]
filterwarnings =
error
ignore::DeprecationWarning
When a warning matches more than one option in the list, the action for the last matching option
is performed.
Both ``-W`` command-line option and ``filterwarnings`` ini option are based on Python's own
`-W option`_ and `warnings.simplefilter`_, so please refer to those sections in the Python
documentation for other examples and advanced usage.
*Credits go to Florian Schulze for the reference implementation in the* `pytest-warnings`_
*plugin.*
.. _`-W option`: https://docs.python.org/3/using/cmdline.html?highlight=#cmdoption-W
.. _warnings.simplefilter: https://docs.python.org/3/library/warnings.html#warnings.simplefilter
.. _`pytest-warnings`: https://github.com/fschulze/pytest-warnings
.. _`asserting warnings`:
.. _assertwarnings:
.. _`asserting warnings with the warns function`:
.. _warns:
Asserting warnings with the warns function
-----------------------------------------------
.. versionadded:: 2.8
You can check that code raises a particular warning using ``pytest.warns``,
which works in a similar manner to :ref:`raises <assertraises>`::
import warnings
import pytest
def test_warning():
with pytest.warns(UserWarning):
warnings.warn("my warning", UserWarning)
The test will fail if the warning in question is not raised.
You can also call ``pytest.warns`` on a function or code string::
pytest.warns(expected_warning, func, *args, **kwargs)
pytest.warns(expected_warning, "func(*args, **kwargs)")
The function also returns a list of all raised warnings (as
``warnings.WarningMessage`` objects), which you can query for
additional information::
with pytest.warns(RuntimeWarning) as record:
warnings.warn("another warning", RuntimeWarning)
# check that only one warning was raised
assert len(record) == 1
# check that the message matches
assert record[0].message.args[0] == "another warning"
Alternatively, you can examine raised warnings in detail using the
:ref:`recwarn <recwarn>` fixture (see below).
.. note::
``DeprecationWarning`` and ``PendingDeprecationWarning`` are treated
differently; see :ref:`ensuring_function_triggers`.
.. _`recording warnings`:
.. _recwarn:
Recording warnings
------------------------
You can record raised warnings either using ``pytest.warns`` or with
the ``recwarn`` fixture.
To record with ``pytest.warns`` without asserting anything about the warnings,
pass ``None`` as the expected warning type::
with pytest.warns(None) as record:
warnings.warn("user", UserWarning)
warnings.warn("runtime", RuntimeWarning)
assert len(record) == 2
assert str(record[0].message) == "user"
assert str(record[1].message) == "runtime"
The ``recwarn`` fixture will record warnings for the whole function::
import warnings
def test_hello(recwarn):
warnings.warn("hello", UserWarning)
assert len(recwarn) == 1
w = recwarn.pop(UserWarning)
assert issubclass(w.category, UserWarning)
assert str(w.message) == "hello"
assert w.filename
assert w.lineno
Both ``recwarn`` and ``pytest.warns`` return the same interface for recorded
warnings: a WarningsRecorder instance. To view the recorded warnings, you can
iterate over this instance, call ``len`` on it to get the number of recorded
warnings, or index into it to get a particular recorded warning. It also
provides these methods:
.. autoclass:: _pytest.recwarn.WarningsRecorder()
:members:
Each recorded warning has the attributes ``message``, ``category``,
``filename``, ``lineno``, ``file``, and ``line``. The ``category`` is the
class of the warning. The ``message`` is the warning itself; calling
``str(message)`` will return the actual message of the warning.
.. note::
:class:`RecordedWarning` was changed from a plain class to a namedtuple in pytest 3.1
.. note::
``DeprecationWarning`` and ``PendingDeprecationWarning`` are treated
differently; see :ref:`ensuring_function_triggers`.
.. _`ensuring a function triggers a deprecation warning`:
.. _ensuring_function_triggers:
Ensuring a function triggers a deprecation warning
-------------------------------------------------------
You can also call a global helper for checking
that a certain function call triggers a ``DeprecationWarning`` or
``PendingDeprecationWarning``::
import pytest
def test_global():
pytest.deprecated_call(myfunction, 17)
By default, ``DeprecationWarning`` and ``PendingDeprecationWarning`` will not be
caught when using ``pytest.warns`` or ``recwarn`` because default Python warnings filters hide
them. If you wish to record them in your own code, use the
command ``warnings.simplefilter('always')``::
import warnings
import pytest
def test_deprecation(recwarn):
warnings.simplefilter('always')
warnings.warn("deprecated", DeprecationWarning)
assert len(recwarn) == 1
assert recwarn.pop(DeprecationWarning)
You can also use it as a contextmanager::
def test_global():
with pytest.deprecated_call():
myobject.deprecated_method()