438 lines
13 KiB
ReStructuredText
438 lines
13 KiB
ReStructuredText
.. _`warnings`:
|
|
|
|
Warnings Capture
|
|
================
|
|
|
|
|
|
|
|
Starting from version ``3.1``, pytest now automatically catches warnings during test execution
|
|
and displays them at the end of the session:
|
|
|
|
.. code-block:: python
|
|
|
|
# content of test_show_warnings.py
|
|
import warnings
|
|
|
|
|
|
def api_v1():
|
|
warnings.warn(UserWarning("api v1, should use functions from v2"))
|
|
return 1
|
|
|
|
|
|
def test_one():
|
|
assert api_v1() == 1
|
|
|
|
Running pytest now produces this output:
|
|
|
|
.. code-block:: pytest
|
|
|
|
$ pytest test_show_warnings.py
|
|
=========================== test session starts ============================
|
|
platform linux -- Python 3.x.y, pytest-5.x.y, py-1.x.y, pluggy-0.x.y
|
|
cachedir: $PYTHON_PREFIX/.pytest_cache
|
|
rootdir: $REGENDOC_TMPDIR
|
|
collected 1 item
|
|
|
|
test_show_warnings.py . [100%]
|
|
|
|
============================= warnings summary =============================
|
|
test_show_warnings.py::test_one
|
|
$REGENDOC_TMPDIR/test_show_warnings.py:5: UserWarning: api v1, should use functions from v2
|
|
warnings.warn(UserWarning("api v1, should use functions from v2"))
|
|
|
|
-- Docs: https://docs.pytest.org/en/latest/warnings.html
|
|
=================== 1 passed, 1 warnings in 0.12 seconds ===================
|
|
|
|
The ``-W`` flag can be passed to control which warnings will be displayed or even turn
|
|
them into errors:
|
|
|
|
.. code-block:: pytest
|
|
|
|
$ pytest -q test_show_warnings.py -W error::UserWarning
|
|
F [100%]
|
|
================================= FAILURES =================================
|
|
_________________________________ test_one _________________________________
|
|
|
|
def test_one():
|
|
> assert api_v1() == 1
|
|
|
|
test_show_warnings.py:10:
|
|
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
|
|
|
|
def api_v1():
|
|
> warnings.warn(UserWarning("api v1, should use functions from v2"))
|
|
E UserWarning: api v1, should use functions from v2
|
|
|
|
test_show_warnings.py:5: UserWarning
|
|
1 failed in 0.12 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 user warnings, but will transform
|
|
all other warnings into errors.
|
|
|
|
.. code-block:: ini
|
|
|
|
[pytest]
|
|
filterwarnings =
|
|
error
|
|
ignore::UserWarning
|
|
|
|
|
|
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.
|
|
|
|
.. _`filterwarnings`:
|
|
|
|
``@pytest.mark.filterwarnings``
|
|
-------------------------------
|
|
|
|
|
|
|
|
You can use the ``@pytest.mark.filterwarnings`` to add warning filters to specific test items,
|
|
allowing you to have finer control of which warnings should be captured at test, class or
|
|
even module level:
|
|
|
|
.. code-block:: python
|
|
|
|
import warnings
|
|
|
|
|
|
def api_v1():
|
|
warnings.warn(UserWarning("api v1, should use functions from v2"))
|
|
return 1
|
|
|
|
|
|
@pytest.mark.filterwarnings("ignore:api v1")
|
|
def test_one():
|
|
assert api_v1() == 1
|
|
|
|
|
|
Filters applied using a mark take precedence over filters passed on the command line or configured
|
|
by the ``filterwarnings`` ini option.
|
|
|
|
You may apply a filter to all tests of a class by using the ``filterwarnings`` mark as a class
|
|
decorator or to all tests in a module by setting the ``pytestmark`` variable:
|
|
|
|
.. code-block:: python
|
|
|
|
# turns all warnings into errors for this module
|
|
pytestmark = pytest.mark.filterwarnings("error")
|
|
|
|
|
|
|
|
*Credits go to Florian Schulze for the reference implementation in the* `pytest-warnings`_
|
|
*plugin.*
|
|
|
|
.. _`-W option`: https://docs.python.org/3/using/cmdline.html#cmdoption-w
|
|
.. _warnings.simplefilter: https://docs.python.org/3/library/warnings.html#warnings.simplefilter
|
|
.. _`pytest-warnings`: https://github.com/fschulze/pytest-warnings
|
|
|
|
Disabling warnings summary
|
|
--------------------------
|
|
|
|
Although not recommended, you can use the ``--disable-warnings`` command-line option to suppress the
|
|
warning summary entirely from the test run output.
|
|
|
|
Disabling warning capture entirely
|
|
----------------------------------
|
|
|
|
This plugin is enabled by default but can be disabled entirely in your ``pytest.ini`` file with:
|
|
|
|
.. code-block:: ini
|
|
|
|
[pytest]
|
|
addopts = -p no:warnings
|
|
|
|
Or passing ``-p no:warnings`` in the command-line. This might be useful if your test suites handles warnings
|
|
using an external system.
|
|
|
|
|
|
.. _`deprecation-warnings`:
|
|
|
|
DeprecationWarning and PendingDeprecationWarning
|
|
------------------------------------------------
|
|
|
|
|
|
|
|
|
|
By default pytest will display ``DeprecationWarning`` and ``PendingDeprecationWarning`` warnings from
|
|
user code and third-party libraries, as recommended by `PEP-0565 <https://www.python.org/dev/peps/pep-0565>`_.
|
|
This helps users keep their code modern and avoid breakages when deprecated warnings are effectively removed.
|
|
|
|
Sometimes it is useful to hide some specific deprecation warnings that happen in code that you have no control over
|
|
(such as third-party libraries), in which case you might use the warning filters options (ini or marks) to ignore
|
|
those warnings.
|
|
|
|
For example:
|
|
|
|
.. code-block:: ini
|
|
|
|
[pytest]
|
|
filterwarnings =
|
|
ignore:.*U.*mode is deprecated:DeprecationWarning
|
|
|
|
|
|
This will ignore all warnings of type ``DeprecationWarning`` where the start of the message matches
|
|
the regular expression ``".*U.*mode is deprecated"``.
|
|
|
|
.. note::
|
|
|
|
If warnings are configured at the interpreter level, using
|
|
the `PYTHONWARNINGS <https://docs.python.org/3/using/cmdline.html#envvar-PYTHONWARNINGS>`_ environment variable or the
|
|
``-W`` command-line option, pytest will not configure any filters by default.
|
|
|
|
Also pytest doesn't follow ``PEP-0506`` suggestion of resetting all warning filters because
|
|
it might break test suites that configure warning filters themselves
|
|
by calling ``warnings.simplefilter`` (see issue `#2430 <https://github.com/pytest-dev/pytest/issues/2430>`_
|
|
for an example of that).
|
|
|
|
|
|
.. _`ensuring a function triggers a deprecation warning`:
|
|
|
|
.. _ensuring_function_triggers:
|
|
|
|
Ensuring code triggers a deprecation warning
|
|
--------------------------------------------
|
|
|
|
You can also call a global helper for checking
|
|
that a certain function call triggers a ``DeprecationWarning`` or
|
|
``PendingDeprecationWarning``:
|
|
|
|
.. code-block:: python
|
|
|
|
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')``:
|
|
|
|
.. code-block:: python
|
|
|
|
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:
|
|
|
|
.. code-block:: python
|
|
|
|
def test_global():
|
|
with pytest.deprecated_call():
|
|
myobject.deprecated_method()
|
|
|
|
|
|
|
|
.. _`asserting warnings`:
|
|
|
|
.. _assertwarnings:
|
|
|
|
.. _`asserting warnings with the warns function`:
|
|
|
|
.. _warns:
|
|
|
|
Asserting warnings with the warns function
|
|
------------------------------------------
|
|
|
|
|
|
|
|
You can check that code raises a particular warning using ``pytest.warns``,
|
|
which works in a similar manner to :ref:`raises <assertraises>`:
|
|
|
|
.. code-block:: python
|
|
|
|
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. The keyword
|
|
argument ``match`` to assert that the exception matches a text or regex::
|
|
|
|
>>> with warns(UserWarning, match='must be 0 or None'):
|
|
... warnings.warn("value must be 0 or None", UserWarning)
|
|
|
|
>>> with warns(UserWarning, match=r'must be \d+$'):
|
|
... warnings.warn("value must be 42", UserWarning)
|
|
|
|
>>> with warns(UserWarning, match=r'must be \d+$'):
|
|
... warnings.warn("this is not here", UserWarning)
|
|
Traceback (most recent call last):
|
|
...
|
|
Failed: DID NOT WARN. No warnings of type ...UserWarning... was emitted...
|
|
|
|
You can also call ``pytest.warns`` on a function or code string::
|
|
|
|
.. code-block:: python
|
|
|
|
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:
|
|
|
|
.. code-block:: python
|
|
|
|
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:
|
|
|
|
.. code-block:: python
|
|
|
|
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:
|
|
|
|
.. code-block:: python
|
|
|
|
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.
|
|
|
|
.. currentmodule:: _pytest.warnings
|
|
|
|
Full API: :class:`WarningsRecorder`.
|
|
|
|
.. _custom_failure_messages:
|
|
|
|
Custom failure messages
|
|
-----------------------
|
|
|
|
Recording warnings provides an opportunity to produce custom test
|
|
failure messages for when no warnings are issued or other conditions
|
|
are met.
|
|
|
|
.. code-block:: python
|
|
|
|
def test():
|
|
with pytest.warns(Warning) as record:
|
|
f()
|
|
if not record:
|
|
pytest.fail("Expected a warning!")
|
|
|
|
If no warnings are issued when calling ``f``, then ``not record`` will
|
|
evaluate to ``True``. You can then call ``pytest.fail`` with a
|
|
custom error message.
|
|
|
|
.. _internal-warnings:
|
|
|
|
Internal pytest warnings
|
|
------------------------
|
|
|
|
|
|
|
|
pytest may generate its own warnings in some situations, such as improper usage or deprecated features.
|
|
|
|
For example, pytest will emit a warning if it encounters a class that matches :confval:`python_classes` but also
|
|
defines an ``__init__`` constructor, as this prevents the class from being instantiated:
|
|
|
|
.. code-block:: python
|
|
|
|
# content of test_pytest_warnings.py
|
|
class Test:
|
|
def __init__(self):
|
|
pass
|
|
|
|
def test_foo(self):
|
|
assert 1 == 1
|
|
|
|
.. code-block:: pytest
|
|
|
|
$ pytest test_pytest_warnings.py -q
|
|
|
|
============================= warnings summary =============================
|
|
test_pytest_warnings.py:1
|
|
$REGENDOC_TMPDIR/test_pytest_warnings.py:1: PytestCollectionWarning: cannot collect test class 'Test' because it has a __init__ constructor (from: test_pytest_warnings.py)
|
|
class Test:
|
|
|
|
-- Docs: https://docs.pytest.org/en/latest/warnings.html
|
|
1 warnings in 0.12 seconds
|
|
|
|
These warnings might be filtered using the same builtin mechanisms used to filter other types of warnings.
|
|
|
|
Please read our :ref:`backwards-compatibility` to learn how we proceed about deprecating and eventually removing
|
|
features.
|
|
|
|
The following warning types are used by pytest and are part of the public API:
|
|
|
|
.. autoclass:: pytest.PytestWarning
|
|
|
|
.. autoclass:: pytest.PytestAssertRewriteWarning
|
|
|
|
.. autoclass:: pytest.PytestCacheWarning
|
|
|
|
.. autoclass:: pytest.PytestCollectionWarning
|
|
|
|
.. autoclass:: pytest.PytestConfigWarning
|
|
|
|
.. autoclass:: pytest.PytestDeprecationWarning
|
|
|
|
.. autoclass:: pytest.PytestExperimentalApiWarning
|
|
|
|
.. autoclass:: pytest.PytestUnhandledCoroutineWarning
|
|
|
|
.. autoclass:: pytest.PytestUnknownMarkWarning
|
|
|
|
.. autoclass:: pytest.RemovedInPytest4Warning
|