diff --git a/lib/matplotlib/tests/test_backend_pdf.py b/lib/matplotlib/tests/test_backend_pdf.py
index d6989066b264..11b4936f7f86 100644
--- a/lib/matplotlib/tests/test_backend_pdf.py
+++ b/lib/matplotlib/tests/test_backend_pdf.py
@@ -3,7 +3,6 @@
 from pathlib import Path
 import sys
 import tempfile
-import warnings
 
 import numpy as np
 import pytest
@@ -14,11 +13,9 @@
 from matplotlib.testing.decorators import image_comparison
 
 
-with warnings.catch_warnings():
-    warnings.simplefilter('ignore')
-    needs_usetex = pytest.mark.skipif(
-        not checkdep_usetex(True),
-        reason="This test needs a TeX installation")
+needs_usetex = pytest.mark.skipif(
+    not checkdep_usetex(True),
+    reason="This test needs a TeX installation")
 
 
 @image_comparison(['pdf_use14corefonts.pdf'])
diff --git a/lib/matplotlib/tests/test_backend_ps.py b/lib/matplotlib/tests/test_backend_ps.py
index 1ce38531af73..5d8d4656b13c 100644
--- a/lib/matplotlib/tests/test_backend_ps.py
+++ b/lib/matplotlib/tests/test_backend_ps.py
@@ -3,7 +3,6 @@
 from pathlib import Path
 import re
 import tempfile
-import warnings
 
 import pytest
 
@@ -13,14 +12,12 @@
 from matplotlib.testing.decorators import image_comparison
 
 
-with warnings.catch_warnings():
-    warnings.simplefilter('ignore')
-    needs_ghostscript = pytest.mark.skipif(
-        "eps" not in mpl.testing.compare.converter,
-        reason="This test needs a ghostscript installation")
-    needs_usetex = pytest.mark.skipif(
-        not mpl.checkdep_usetex(True),
-        reason="This test needs a TeX installation")
+needs_ghostscript = pytest.mark.skipif(
+    "eps" not in mpl.testing.compare.converter,
+    reason="This test needs a ghostscript installation")
+needs_usetex = pytest.mark.skipif(
+    not mpl.checkdep_usetex(True),
+    reason="This test needs a TeX installation")
 
 
 # This tests tends to hit a TeX cache lock on AppVeyor.
diff --git a/lib/matplotlib/tests/test_backend_svg.py b/lib/matplotlib/tests/test_backend_svg.py
index 642975b68177..5c27149b725d 100644
--- a/lib/matplotlib/tests/test_backend_svg.py
+++ b/lib/matplotlib/tests/test_backend_svg.py
@@ -2,7 +2,6 @@
 from io import BytesIO
 import re
 import tempfile
-import warnings
 import xml.parsers.expat
 
 import pytest
@@ -14,11 +13,9 @@
 from matplotlib.testing.decorators import image_comparison
 
 
-with warnings.catch_warnings():
-    warnings.simplefilter('ignore')
-    needs_usetex = pytest.mark.skipif(
-        not mpl.checkdep_usetex(True),
-        reason="This test needs a TeX installation")
+needs_usetex = pytest.mark.skipif(
+    not mpl.checkdep_usetex(True),
+    reason="This test needs a TeX installation")
 
 
 def test_visibility():
diff --git a/lib/matplotlib/tests/test_cbook.py b/lib/matplotlib/tests/test_cbook.py
index 3c46550c9176..82aec8495845 100644
--- a/lib/matplotlib/tests/test_cbook.py
+++ b/lib/matplotlib/tests/test_cbook.py
@@ -434,7 +434,7 @@ def test_step_fails(args):
 
 
 def test_grouper():
-    class dummy():
+    class dummy:
         pass
     a, b, c, d, e = objs = [dummy() for j in range(5)]
     g = cbook.Grouper()
@@ -454,7 +454,7 @@ class dummy():
 
 
 def test_grouper_private():
-    class dummy():
+    class dummy:
         pass
     objs = [dummy() for j in range(5)]
     g = cbook.Grouper()
@@ -484,7 +484,7 @@ def test_flatiter():
 
 def test_reshape2d():
 
-    class dummy():
+    class dummy:
         pass
 
     xnew = cbook._reshape_2D([], 'x')
diff --git a/lib/matplotlib/tests/test_text.py b/lib/matplotlib/tests/test_text.py
index f10a97844e6c..fb2d62e075a3 100644
--- a/lib/matplotlib/tests/test_text.py
+++ b/lib/matplotlib/tests/test_text.py
@@ -12,11 +12,9 @@
 from matplotlib.testing.decorators import image_comparison
 
 
-with warnings.catch_warnings():
-    warnings.simplefilter('ignore')
-    needs_usetex = pytest.mark.skipif(
-        not matplotlib.checkdep_usetex(True),
-        reason="This test needs a TeX installation")
+needs_usetex = pytest.mark.skipif(
+    not matplotlib.checkdep_usetex(True),
+    reason="This test needs a TeX installation")
 
 
 @image_comparison(['font_styles'])
diff --git a/lib/matplotlib/tests/test_ticker.py b/lib/matplotlib/tests/test_ticker.py
index 05c553ae2b07..2dfe2329a139 100644
--- a/lib/matplotlib/tests/test_ticker.py
+++ b/lib/matplotlib/tests/test_ticker.py
@@ -1,4 +1,7 @@
-import warnings
+try:
+    from contextlib import nullcontext
+except ImportError:
+    from contextlib import ExitStack as nullcontext  # Py 3.6.
 import re
 
 import numpy as np
@@ -242,9 +245,8 @@ def test_set_params(self):
 class _LogitHelper:
     @staticmethod
     def isclose(x, y):
-        if x >= 1 or x <= 0 or y >= 1 or y <= 0:
-            return False
-        return np.isclose(-np.log(1/x-1), -np.log(1/y-1))
+        return (np.isclose(-np.log(1/x-1), -np.log(1/y-1))
+                if 0 < x < 1 and 0 < y < 1 else False)
 
     @staticmethod
     def assert_almost_equal(x, y):
@@ -460,19 +462,15 @@ def test_offset_value(self, left, right, offset):
         fig, ax = plt.subplots()
         formatter = ax.get_xaxis().get_major_formatter()
 
-        with warnings.catch_warnings(record=True) as w:
-            warnings.filterwarnings('always', 'Attempting to set identical',
-                                    UserWarning)
+        with (pytest.warns(UserWarning, match='Attempting to set identical')
+              if left == right else nullcontext()):
             ax.set_xlim(left, right)
-        assert len(w) == (1 if left == right else 0)
         ax.get_xaxis()._update_ticks()
         assert formatter.offset == offset
 
-        with warnings.catch_warnings(record=True) as w:
-            warnings.filterwarnings('always', 'Attempting to set identical',
-                                    UserWarning)
+        with (pytest.warns(UserWarning, match='Attempting to set identical')
+              if left == right else nullcontext()):
             ax.set_xlim(right, left)
-        assert len(w) == (1 if left == right else 0)
         ax.get_xaxis()._update_ticks()
         assert formatter.offset == offset
 
@@ -484,8 +482,7 @@ def test_use_offset(self, use_offset):
 
     @pytest.mark.parametrize(
         'sci_type, scilimits, lim, orderOfMag, fewticks', scilimits_data)
-    def test_scilimits(self, sci_type, scilimits, lim, orderOfMag,
-                       fewticks):
+    def test_scilimits(self, sci_type, scilimits, lim, orderOfMag, fewticks):
         tmp_form = mticker.ScalarFormatter()
         tmp_form.set_scientific(sci_type)
         tmp_form.set_powerlimits(scilimits)
@@ -542,7 +539,7 @@ def test_blank(self):
         assert formatter(10**0.1) == ''
 
 
-class TestLogFormatterMathtext():
+class TestLogFormatterMathtext:
     fmt = mticker.LogFormatterMathtext()
     test_data = [
         (0, 1, '$\\mathdefault{10^{0}}$'),
diff --git a/lib/matplotlib/tests/test_transforms.py b/lib/matplotlib/tests/test_transforms.py
index b0cb3b653c7b..f35467ee7206 100644
--- a/lib/matplotlib/tests/test_transforms.py
+++ b/lib/matplotlib/tests/test_transforms.py
@@ -228,7 +228,7 @@ def transform_path_non_affine(self, path):
         return self.real_trans.transform_path(path)
 
 
-class TestBasicTransform():
+class TestBasicTransform:
     def setup_method(self):
 
         self.ta1 = mtransforms.Affine2D(shorthand_name='ta1').rotate(np.pi / 2)
diff --git a/lib/matplotlib/tight_layout.py b/lib/matplotlib/tight_layout.py
index 9cddeed3d5c5..f613450a93a7 100644
--- a/lib/matplotlib/tight_layout.py
+++ b/lib/matplotlib/tight_layout.py
@@ -220,9 +220,8 @@ def get_renderer(fig):
 
         if canvas and hasattr(canvas, "get_renderer"):
             renderer = canvas.get_renderer()
-        else:
-            # not sure if this can happen
-            cbook._warn_external("tight_layout : falling back to Agg renderer")
+        else:  # Some noninteractive backends have no renderer until draw time.
+            cbook._warn_external("tight_layout: falling back to Agg renderer")
             from matplotlib.backends.backend_agg import FigureCanvasAgg
             canvas = FigureCanvasAgg(fig)
             renderer = canvas.get_renderer()
diff --git a/lib/matplotlib/tri/triinterpolate.py b/lib/matplotlib/tri/triinterpolate.py
index e23c23ce35c4..9188d6d2643b 100644
--- a/lib/matplotlib/tri/triinterpolate.py
+++ b/lib/matplotlib/tri/triinterpolate.py
@@ -588,7 +588,7 @@ def _compute_tri_eccentricities(tris_pts):
 
 # FEM element used for interpolation and for solving minimisation
 # problem (Reduced HCT element)
-class _ReducedHCT_Element():
+class _ReducedHCT_Element:
     """
     Implementation of reduced HCT triangular element with explicit shape
     functions.
@@ -1006,7 +1006,7 @@ def get_Kff_and_Ff(self, J, ecc, triangles, Uc):
 # _DOF_estimator_min_E
 # Private classes used to compute the degree of freedom of each triangular
 # element for the TriCubicInterpolator.
-class _DOF_estimator():
+class _DOF_estimator:
     """
     Abstract base class for classes used to perform estimation of a function
     first derivatives, and deduce the dofs for a CubicTriInterpolator using a