Cleanup warnings handling in tests.

anntzer · anntzer · commit 359f76af2db4 · 2019-03-02T12:20:50.000+01:00
This caught two "incorrect" tests:

- in test_style.py::test_invalid_rc_warning_includes_filename, the
  `for w in warns: ...` assertion did nothing as no warning was
  emitted so `warns` was empty (instead, the message is just print()ed
  to stderr.
- in test_image.py::test_empty_imshow, the caught warning message was
  missing spaces around the equals.
diff --git a/lib/matplotlib/tests/test_axes.py b/lib/matplotlib/tests/test_axes.py
@@ -5233,9 +5233,8 @@ def generate_errorbar_inputs():
 
 @pytest.mark.parametrize('kwargs', generate_errorbar_inputs())
 def test_errorbar_inputs_shotgun(kwargs):
-    with warnings.catch_warnings():
-        # (n, 1)-shaped error deprecation already tested by test_errorbar.
-        warnings.simplefilter("ignore", MatplotlibDeprecationWarning)
+    # (n, 1)-shaped error deprecation already tested by test_errorbar.
+    with mpl.cbook._suppress_matplotlib_deprecation_warning():
         ax = plt.gca()
         eb = ax.errorbar(**kwargs)
         eb.remove()
diff --git a/lib/matplotlib/tests/test_figure.py b/lib/matplotlib/tests/test_figure.py
@@ -1,6 +1,5 @@
 from pathlib import Path
 import platform
-import warnings
 
 from matplotlib import rcParams
 from matplotlib.testing.decorators import image_comparison, check_figures_equal
@@ -154,11 +153,9 @@ def test_gca():
 
     # the final request for a polar axes will end up creating one
     # with a spec of 111.
-    with warnings.catch_warnings(record=True) as w:
-        warnings.simplefilter('always')
+    with pytest.warns(UserWarning):
         # Changing the projection will throw a warning
         assert fig.gca(polar=True) is not ax3
-        assert len(w) == 1
     assert fig.gca(polar=True) is not ax2
     assert fig.gca().get_geometry() == (1, 1, 1)
 
@@ -204,11 +201,9 @@ def test_alpha():
 
 
 def test_too_many_figures():
-    with warnings.catch_warnings(record=True) as w:
-        warnings.simplefilter("always")
+    with pytest.warns(RuntimeWarning):
         for i in range(rcParams['figure.max_open_warning'] + 1):
             plt.figure()
-        assert len(w) == 1
 
 
 def test_iterability_axes_argument():
diff --git a/lib/matplotlib/tests/test_image.py b/lib/matplotlib/tests/test_image.py
@@ -894,9 +894,8 @@ def test_imshow_bignumbers_real():
      lambda: colors.PowerNorm(1)])
 def test_empty_imshow(make_norm):
     fig, ax = plt.subplots()
-    with warnings.catch_warnings():
-        warnings.filterwarnings(
-            "ignore", "Attempting to set identical left==right")
+    with pytest.warns(UserWarning,
+                      match="Attempting to set identical left == right"):
         im = ax.imshow([[]], norm=make_norm())
     im.set_extent([-5, 5, -5, 5])
     fig.canvas.draw()
diff --git a/lib/matplotlib/tests/test_mlab.py b/lib/matplotlib/tests/test_mlab.py
@@ -1,5 +1,4 @@
 import tempfile
-import warnings
 
 from numpy.testing import (assert_allclose, assert_almost_equal,
                            assert_array_equal, assert_array_almost_equal_nulp)
@@ -1859,13 +1858,9 @@ def test_specgram_phase(self):
         assert spec.shape[1] == self.t_specgram.shape[0]
 
     def test_specgram_warn_only1seg(self):
-        """Warning should be raised if len(x) <= NFFT. """
-        with warnings.catch_warnings(record=True) as w:
-            warnings.simplefilter("always", category=UserWarning)
+        """Warning should be raised if len(x) <= NFFT."""
+        with pytest.warns(UserWarning, match="Only one segment is calculated"):
             mlab.specgram(x=self.y, NFFT=len(self.y), Fs=self.Fs)
-        assert len(w) == 1
-        assert issubclass(w[0].category, UserWarning)
-        assert str(w[0].message).startswith("Only one segment is calculated")
 
     def test_psd_csd_equal(self):
         freqs = self.freqs_density
diff --git a/lib/matplotlib/tests/test_rcparams.py b/lib/matplotlib/tests/test_rcparams.py
@@ -2,13 +2,12 @@
 import copy
 import os
 from unittest import mock
-import warnings
 
 from cycler import cycler, Cycler
 import pytest
 
 import matplotlib as mpl
-from matplotlib.cbook import MatplotlibDeprecationWarning
+from matplotlib import cbook
 import matplotlib.pyplot as plt
 import matplotlib.colors as mcolors
 import numpy as np
@@ -91,22 +90,15 @@ def test_rcparams_update():
     rc = mpl.RcParams({'figure.figsize': (3.5, 42)})
     bad_dict = {'figure.figsize': (3.5, 42, 1)}
     # make sure validation happens on input
-    with pytest.raises(ValueError):
-
-        with warnings.catch_warnings():
-            warnings.filterwarnings('ignore',
-                                message='.*(validate)',
-                                category=UserWarning)
-            rc.update(bad_dict)
+    with pytest.raises(ValueError), \
+         pytest.warns(UserWarning, match="validate"):
+        rc.update(bad_dict)
 
 
 def test_rcparams_init():
-    with pytest.raises(ValueError):
-        with warnings.catch_warnings():
-            warnings.filterwarnings('ignore',
-                                message='.*(validate)',
-                                category=UserWarning)
-            mpl.RcParams({'figure.figsize': (3.5, 42, 1)})
+    with pytest.raises(ValueError), \
+         pytest.warns(UserWarning, match="validate"):
+        mpl.RcParams({'figure.figsize': (3.5, 42, 1)})
 
 
 def test_Bug_2543():
@@ -117,9 +109,7 @@ def test_Bug_2543():
     # We filter warnings at this stage since a number of them are raised
     # for deprecated rcparams as they should. We don't want these in the
     # printed in the test suite.
-    with warnings.catch_warnings():
-        warnings.filterwarnings('ignore',
-                                category=MatplotlibDeprecationWarning)
+    with cbook._suppress_matplotlib_deprecation_warning():
         with mpl.rc_context():
             _copy = mpl.rcParams.copy()
             for key in _copy:
diff --git a/lib/matplotlib/tests/test_style.py b/lib/matplotlib/tests/test_style.py
@@ -3,7 +3,6 @@
 import gc
 from pathlib import Path
 from tempfile import TemporaryDirectory
-import warnings
 
 import pytest
 
@@ -36,16 +35,13 @@ def temp_style(style_name, settings=None):
         style.reload_library()
 
 
-def test_invalid_rc_warning_includes_filename():
+def test_invalid_rc_warning_includes_filename(capsys):
     SETTINGS = {'foo': 'bar'}
     basename = 'basename'
-    with warnings.catch_warnings(record=True) as warns:
-        with temp_style(basename, SETTINGS):
-            # style.reload_library() in temp_style() triggers the warning
-            pass
-
-    for w in warns:
-        assert basename in str(w.message)
+    with temp_style(basename, SETTINGS):
+        # style.reload_library() in temp_style() triggers the warning
+        pass
+    assert basename in capsys.readouterr().err
 
 
 def test_available():
diff --git a/lib/matplotlib/tests/test_subplots.py b/lib/matplotlib/tests/test_subplots.py
@@ -1,5 +1,4 @@
 import itertools
-import warnings
 
 import numpy
 import matplotlib.pyplot as plt
@@ -122,16 +121,15 @@ def test_exceptions():
         plt.subplots(2, 2, sharey='blah')
     # We filter warnings in this test which are genuine since
     # the point of this test is to ensure that this raises.
-    with warnings.catch_warnings():
-        warnings.filterwarnings('ignore',
-                                message='.*sharex argument to subplots',
-                                category=UserWarning)
-        with pytest.raises(ValueError):
-            plt.subplots(2, 2, -1)
-        with pytest.raises(ValueError):
-            plt.subplots(2, 2, 0)
-        with pytest.raises(ValueError):
-            plt.subplots(2, 2, 5)
+    with pytest.warns(UserWarning, match='.*sharex argument to subplots'), \
+         pytest.raises(ValueError):
+        plt.subplots(2, 2, -1)
+    with pytest.warns(UserWarning, match='.*sharex argument to subplots'), \
+         pytest.raises(ValueError):
+        plt.subplots(2, 2, 0)
+    with pytest.warns(UserWarning, match='.*sharex argument to subplots'), \
+         pytest.raises(ValueError):
+        plt.subplots(2, 2, 5)
 
 
 @image_comparison(baseline_images=['subplots_offset_text'], remove_text=False)
diff --git a/lib/matplotlib/tests/test_ticker.py b/lib/matplotlib/tests/test_ticker.py
@@ -233,10 +233,8 @@ def test_set_params(self):
         Should not exception, and should raise a warning.
         """
         loc = mticker.NullLocator()
-        with warnings.catch_warnings(record=True) as w:
-            warnings.simplefilter("always")
+        with pytest.warns(UserWarning):
             loc.set_params()
-            assert len(w) == 1
 
 
 class TestLogitLocator(object):
diff --git a/lib/matplotlib/tests/test_tightlayout.py b/lib/matplotlib/tests/test_tightlayout.py
@@ -2,6 +2,7 @@
 
 import numpy as np
 from numpy.testing import assert_array_equal
+import pytest
 
 from matplotlib.testing.decorators import image_comparison
 import matplotlib.pyplot as plt
@@ -267,50 +268,36 @@ def _subplots():
 
 
 def test_empty_layout():
-    """Tests that tight layout doesn't cause an error when there are
-    no axes.
-    """
-
+    """Test that tight layout doesn't cause an error when there are no axes."""
     fig = plt.gcf()
     fig.tight_layout()
 
 
-def test_verybig_decorators_horizontal():
-    "Test that warning emitted when xlabel too big"
-    fig, ax = plt.subplots(figsize=(3, 2))
-    ax.set_xlabel('a' * 100)
-    with warnings.catch_warnings(record=True) as w:
-        fig.tight_layout()
-        assert len(w) == 1
-
-
-def test_verybig_decorators_vertical():
-    "Test that warning emitted when xlabel too big"
+@pytest.mark.parametrize("label", ["xlabel", "ylabel"])
+def test_verybig_decorators(label):
+    """Test that warning emitted when xlabel/ylabel too big."""
     fig, ax = plt.subplots(figsize=(3, 2))
-    ax.set_ylabel('a' * 100)
-    with warnings.catch_warnings(record=True) as w:
+    ax.set(**{label: 'a' * 100})
+    with pytest.warns(UserWarning):
         fig.tight_layout()
-        assert len(w) == 1
 
 
 def test_big_decorators_horizontal():
     "Test that warning emitted when xlabel too big"
     fig, axs = plt.subplots(1, 2, figsize=(3, 2))
     axs[0].set_xlabel('a' * 30)
     axs[1].set_xlabel('b' * 30)
-    with warnings.catch_warnings(record=True) as w:
+    with pytest.warns(UserWarning):
         fig.tight_layout()
-        assert len(w) == 1
 
 
 def test_big_decorators_vertical():
     "Test that warning emitted when xlabel too big"
     fig, axs = plt.subplots(2, 1, figsize=(3, 2))
     axs[0].set_ylabel('a' * 20)
     axs[1].set_ylabel('b' * 20)
-    with warnings.catch_warnings(record=True) as w:
+    with pytest.warns(UserWarning):
         fig.tight_layout()
-        assert len(w) == 1
 
 
 def test_badsubplotgrid():
@@ -319,9 +306,8 @@ def test_badsubplotgrid():
     ax1 = plt.subplot2grid((4, 5), (0, 0))
     # this is the bad entry:
     ax5 = plt.subplot2grid((5, 5), (0, 3), colspan=3, rowspan=5)
-    with warnings.catch_warnings(record=True) as w:
+    with pytest.warns(UserWarning):
         plt.tight_layout()
-        assert len(w) == 1
 
 
 def test_collapsed():
@@ -333,8 +319,7 @@ def test_collapsed():
 
     ax.annotate('BIG LONG STRING', xy=(1.25, 2), xytext=(10.5, 1.75),)
     p1 = ax.get_position()
-    with warnings.catch_warnings(record=True) as w:
+    with pytest.warns(UserWarning):
         plt.tight_layout()
         p2 = ax.get_position()
         assert p1.width == p2.width
-        assert len(w) == 1
