add pytest cov for warning filter, fix filterwarnings

Author: mroeschke

.github/workflows/unit-tests.yml

@@ -253,7 +253,7 @@ jobs:
           . ~/virtualenvs/pandas-dev/bin/activate
           python -m pip install --no-cache-dir -U pip wheel meson[ninja]==1.2.1 meson-python==0.13.1
           python -m pip install numpy -Csetup-args="-Dallow-noblas=true"
-          python -m pip install --no-cache-dir versioneer[toml] cython python-dateutil pytest>=8.3.4 pytest-xdist>=3.6.1 hypothesis>=6.116.0
+          python -m pip install --no-cache-dir versioneer[toml] cython python-dateutil pytest>=8.3.4 pytest-xdist>=3.6.1 hypothesis>=6.116.0 pytest-cov
           python -m pip install --no-cache-dir --no-build-isolation -e . -Csetup-args="--werror"
           python -m pip list --no-cache-dir
           PANDAS_CI=1 python -m pytest -m 'not slow and not network and not clipboard and not single_cpu' pandas --junitxml=test-data.xml
@@ -292,7 +292,7 @@ jobs:
           /opt/python/cp313-cp313/bin/python -m venv ~/virtualenvs/pandas-dev
           . ~/virtualenvs/pandas-dev/bin/activate
           python -m pip install --no-cache-dir -U pip wheel meson-python==0.13.1 meson[ninja]==1.2.1
-          python -m pip install --no-cache-dir versioneer[toml] cython numpy python-dateutil pytest>=8.3.4 pytest-xdist>=3.6.1 hypothesis>=6.116.0
+          python -m pip install --no-cache-dir versioneer[toml] cython numpy python-dateutil pytest>=8.3.4 pytest-xdist>=3.6.1 hypothesis>=6.116.0 pytest-cov
           python -m pip install --no-cache-dir --no-build-isolation -e . -Csetup-args="--werror"
           python -m pip list --no-cache-dir
 
@@ -432,7 +432,7 @@ jobs:
           PANDAS_CI: 1
         run: |
           source .venv-pyodide/bin/activate
-          pip install pytest hypothesis
+          pip install pytest hypothesis pytest-cov
           # do not import pandas from the checked out repo
           cd ..
           python -c 'import pandas as pd; pd.test(extra_args=["-m not clipboard and not single_cpu and not slow and not network and not db"])'

pandas/tests/reductions/test_reductions.py

@@ -782,7 +782,7 @@ def test_var_masked_array(self, ddof, exp):
         assert result == result_numpy_dtype
         assert result == exp
 
-    @pytest.mark.filterwarning(
+    @pytest.mark.filterwarnings(
         "ignore:Casting complex values to real discards:numpy.exceptions.ComplexWarning"
     )
     def test_var_complex_array(self):