Avoid PytestRemovedIn8Warning for pytest.warns(None)

Details: https://docs.pytest.org/en/latest/how-to/capture-warnings.html#additional-use-cases-of-warnings-in-tests
murrayrm · Jun 16, 2022 · Jun 16, 2022 · Jun 16, 2022 · Jun 16, 2022 · Jun 16, 2022
commit 7f883f67b7f0e2782a1fa8e965b9e9bd7dbd691d
diff --git a/control/tests/iosys_test.py b/control/tests/iosys_test.py
@@ -9,6 +9,7 @@
 """
 
 import re
+import warnings
 
 import numpy as np
 import pytest
@@ -17,6 +18,7 @@
 from control import iosys as ios
 from control.tests.conftest import matrixfilter
 
+
 class TestIOSys:
 
     @pytest.fixture
@@ -1416,11 +1418,10 @@ def test_duplicates(self, tsys):
         nlios2 = ios.NonlinearIOSystem(None,
                                        lambda t, x, u, params: u * u,
                                        inputs=1, outputs=1, name="nlios2")
-        with pytest.warns(None) as record:
+        with warnings.catch_warnings():
+            warnings.simplefilter("error")
             ct.InterconnectedSystem([nlios1, iosys_siso, nlios2],
                                     inputs=0, outputs=0, states=0)
-        if record:
-            pytest.fail("Warning not expected: " + record[0].message)
 
 
 def test_linear_interconnection():
@@ -1510,7 +1511,7 @@ def predprey(t, x, u, params={}):
 
 def pvtol(t, x, u, params={}):
     """Reduced planar vertical takeoff and landing dynamics"""
-    from math import sin, cos
+    from math import cos, sin
     m = params.get('m', 4.)      # kg, system mass
     J = params.get('J', 0.0475)  # kg m^2, system inertia
     r = params.get('r', 0.25)    # m, thrust offset
@@ -1526,7 +1527,7 @@ def pvtol(t, x, u, params={}):
 
 
 def pvtol_full(t, x, u, params={}):
-    from math import sin, cos
+    from math import cos, sin
     m = params.get('m', 4.)      # kg, system mass
     J = params.get('J', 0.0475)  # kg m^2, system inertia
     r = params.get('r', 0.25)    # m, thrust offset
@@ -1579,8 +1580,12 @@ def test_interconnect_unused_input():
                             inputs=['r'],
                             outputs=['y'])
 
-    with pytest.warns(None) as record:
+    with warnings.catch_warnings():
         # no warning if output explicitly ignored, various argument forms
+        warnings.simplefilter("error")
+        # strip out matrix warnings
+        warnings.filterwarnings("ignore", "the matrix subclass",
+                                category=PendingDeprecationWarning)
         h = ct.interconnect([g,s,k],
                             inputs=['r'],
                             outputs=['y'],
@@ -1595,14 +1600,6 @@ def test_interconnect_unused_input():
         h = ct.interconnect([g,s,k],
                             connections=False)
 
-        #https://docs.pytest.org/en/6.2.x/warnings.html#recwarn
-        for r in record:
-            # strip out matrix warnings
-            if re.match(r'.*matrix subclass', str(r.message)):
-                continue
-            print(r.message)
-            pytest.fail(f'Unexpected warning: {r.message}')
-
 
     # warn if explicity ignored input in fact used
     with pytest.warns(
@@ -1657,7 +1654,11 @@ def test_interconnect_unused_output():
 
 
     # no warning if output explicitly ignored
-    with pytest.warns(None) as record:
+    with warnings.catch_warnings():
+        warnings.simplefilter("error")
+        # strip out matrix warnings
+        warnings.filterwarnings("ignore", "the matrix subclass",
+                                category=PendingDeprecationWarning)
         h = ct.interconnect([g,s,k],
                             inputs=['r'],
                             outputs=['y'],
@@ -1672,14 +1673,6 @@ def test_interconnect_unused_output():
         h = ct.interconnect([g,s,k],
                             connections=False)
 
-        #https://docs.pytest.org/en/6.2.x/warnings.html#recwarn
-        for r in record:
-            # strip out matrix warnings
-            if re.match(r'.*matrix subclass', str(r.message)):
-                continue
-            print(r.message)
-            pytest.fail(f'Unexpected warning: {r.message}')
-
     # warn if explicity ignored output in fact used
     with pytest.warns(
             UserWarning,

diff --git a/control/tests/namedio_test.py b/control/tests/namedio_test.py
@@ -10,6 +10,7 @@
 
 import re
 from copy import copy
+import warnings
 
 import numpy as np
 import control as ct
@@ -243,9 +244,12 @@ def test_duplicate_sysname():
     sys = ct.rss(4, 1, 1)
 
     # No warnings should be generated if we reuse an an unnamed system
-    with pytest.warns(None) as record:
+    with warnings.catch_warnings():
+        warnings.simplefilter("error")
+        # strip out matrix warnings
+        warnings.filterwarnings("ignore", "the matrix subclass",
+                                category=PendingDeprecationWarning)
         res = sys * sys
-    assert not any([type(msg) == UserWarning for msg in record])
 
     # Generate a warning if the system is named
     sys = ct.rss(4, 1, 1, name='sys')

diff --git a/control/tests/nyquist_test.py b/control/tests/nyquist_test.py
@@ -8,6 +8,8 @@
 
 """
 
+import warnings
+
 import pytest
 import numpy as np
 import matplotlib.pyplot as plt
@@ -225,10 +227,11 @@ def test_nyquist_encirclements():
     sys = 1 / (s**2 + s + 1)
     with pytest.warns(UserWarning, match="encirclements was a non-integer"):
         count = ct.nyquist_plot(sys, omega_limits=[0.5, 1e3])
-    with pytest.warns(None) as records:
+    with warnings.catch_warnings():
+        warnings.simplefilter("error")
+        # strip out matrix warnings
         count = ct.nyquist_plot(
             sys, omega_limits=[0.5, 1e3], encirclement_threshold=0.2)
-    assert len(records) == 0
     plt.title("Non-integer number of encirclements [%g]" % count)