Merge pull request #2598 from nicoddemus/filterwarnings-mark

Introduce filter-warnings mark

Author: RonnyPfannschmidt

_pytest/warnings.py

@@ -59,6 +59,11 @@ def catch_warnings_for_item(item):
         for arg in inifilters:
             _setoption(warnings, arg)
 
+        mark = item.get_marker('filterwarnings')
+        if mark:
+            for arg in mark.args:
+                warnings._setoption(arg)
+
         yield
 
         for warning in log:

changelog/2598.feature

@@ -0,0 +1,2 @@
+Introduced ``@pytest.mark.filterwarnings`` mark which allows overwriting the warnings filter on a per test, class or module level.
+See the `docs <https://docs.pytest.org/en/latest/warnings.html#pytest-mark-filterwarnings>`_ for more information.

doc/en/warnings.rst

@@ -78,6 +78,40 @@ Both ``-W`` command-line option and ``filterwarnings`` ini option are based on P
 `-W option`_ and `warnings.simplefilter`_, so please refer to those sections in the Python
 documentation for other examples and advanced usage.
 
+``@pytest.mark.filterwarnings``
+-------------------------------
+
+.. versionadded:: 3.2
+
+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')
+
+
 .. note::
 
     ``DeprecationWarning`` and ``PendingDeprecationWarning`` are hidden by the standard library

testing/test_warnings.py

@@ -188,3 +188,32 @@ def test_my_warning(self):
     result.stdout.fnmatch_lines([
         '*== 1 passed in *',
     ])
+
+
+@pytest.mark.parametrize('default_config', ['ini', 'cmdline'])
+def test_filterwarnings_mark(testdir, default_config):
+    """
+    Test ``filterwarnings`` mark works and takes precedence over command line and ini options.
+    """
+    if default_config == 'ini':
+        testdir.makeini("""
+            [pytest]
+            filterwarnings = always
+        """)
+    testdir.makepyfile("""
+        import warnings
+        import pytest
+
+        @pytest.mark.filterwarnings('ignore::RuntimeWarning')
+        def test_ignore_runtime_warning():
+            warnings.warn(RuntimeWarning())
+
+        @pytest.mark.filterwarnings('error')
+        def test_warning_error():
+            warnings.warn(RuntimeWarning())
+
+        def test_show_warning():
+            warnings.warn(RuntimeWarning())
+    """)
+    result = testdir.runpytest('-W always' if default_config == 'cmdline' else '')
+    result.stdout.fnmatch_lines(['*= 1 failed, 2 passed, 1 warnings in *'])