python-control · murrayrm · Mar 31, 2024 · Mar 31, 2024
diff --git a/control/tests/freqresp_test.py b/control/tests/freqresp_test.py
@@ -6,19 +6,21 @@
 including bode plots.
 """
 
+import math
+import re
+
 import matplotlib.pyplot as plt
 import numpy as np
-from numpy.testing import assert_allclose
-import math
 import pytest
+from numpy.testing import assert_allclose
 
 import control as ctrl
+from control.freqplot import (bode_plot, nyquist_plot, nyquist_response,
+                              singular_values_plot, singular_values_response)
+from control.matlab import bode, rss, ss, tf
 from control.statesp import StateSpace
-from control.xferfcn import TransferFunction
-from control.matlab import ss, tf, bode, rss
-from control.freqplot import bode_plot, nyquist_plot, nyquist_response, \
-    singular_values_plot, singular_values_response
 from control.tests.conftest import slycotonly
+from control.xferfcn import TransferFunction
 
 pytestmark = pytest.mark.usefixtures("mplcleanup")
 
@@ -101,12 +103,17 @@ def test_nyquist_basic(ss_siso):
     response = nyquist_response(tf_siso, omega_num=20)
     assert len(response.contour) == 20
 
-    with pytest.warns(UserWarning, match="encirclements was a non-integer"):
+    with pytest.warns() as record:
         count, contour = nyquist_plot(
             tf_siso, plot=False, omega_limits=(1, 100), return_contour=True)
     assert_allclose(contour[0], 1j)
     assert_allclose(contour[-1], 100j)
 
+    # Check known warnings happened as expected
+    assert len(record) == 2
+    assert re.search("encirclements was a non-integer", str(record[0].message))
+    assert re.search("return values .* deprecated", str(record[1].message))
+
     response = nyquist_response(tf_siso, omega=np.logspace(-1, 1, 10))
     assert len(response.contour) == 10
 
@@ -428,14 +435,25 @@ def test_freqresp_warn_infinite():
     np.testing.assert_almost_equal(sys_finite(0, warn_infinite=True), 100)
 
     # Transfer function with infinite zero frequency gain
-    with pytest.warns(RuntimeWarning, match="divide by zero"):
+    with pytest.warns() as record:
         np.testing.assert_almost_equal(
             sys_infinite(0), complex(np.inf, np.nan))
-    with pytest.warns(RuntimeWarning, match="divide by zero"):
+    assert len(record) == 2     # generates two RuntimeWarnings
+    assert record[0].category is RuntimeWarning
+    assert re.search("divide by zero", str(record[0].message))
+    assert record[1].category is RuntimeWarning
+    assert re.search("invalid value", str(record[1].message))
+
+    with pytest.warns() as record:
         np.testing.assert_almost_equal(
             sys_infinite(0, warn_infinite=True), complex(np.inf, np.nan))
     np.testing.assert_almost_equal(
         sys_infinite(0, warn_infinite=False), complex(np.inf, np.nan))
+    assert len(record) == 2     # generates two RuntimeWarnings
+    assert record[0].category is RuntimeWarning
+    assert re.search("divide by zero", str(record[0].message))
+    assert record[1].category is RuntimeWarning
+    assert re.search("invalid value", str(record[1].message))
 
     # Switch to state space
     sys_finite = ctrl.tf2ss(sys_finite)

diff --git a/control/tests/nyquist_test.py b/control/tests/nyquist_test.py
@@ -8,11 +8,13 @@
 
 """
 
+import re
 import warnings
 
-import pytest
-import numpy as np
 import matplotlib.pyplot as plt
+import numpy as np
+import pytest
+
 import control as ct
 
 pytestmark = pytest.mark.usefixtures("mplcleanup")
@@ -66,9 +68,12 @@ def test_nyquist_basic():
     assert _Z(sys) == N_sys + _P(sys)
 
     # With a larger indent_radius, we get a warning message + wrong answer
-    with pytest.warns(UserWarning, match="contour may miss closed loop pole"):
+    with pytest.warns() as rec:
         N_sys = ct.nyquist_response(sys, indent_radius=0.2)
         assert _Z(sys) != N_sys + _P(sys)
+    assert len(rec) == 2
+    assert re.search("contour may miss closed loop pole", str(rec[0].message))
+    assert re.search("encirclements does not match", str(rec[1].message))
 
     # Unstable system
     sys = ct.tf([10], [1, 2, 2, 1])
@@ -104,11 +109,15 @@ def test_nyquist_basic():
         sys, np.linspace(1e-4, 1e2, 100), indent_radius=1e-2,
         return_contour=True)
     assert not all(contour_indented.real == 0)
-    with pytest.warns(UserWarning, match="encirclements does not match"):
+
+    with pytest.warns() as record:
         count, contour = ct.nyquist_response(
             sys, np.linspace(1e-4, 1e2, 100), indent_radius=1e-2,
             return_contour=True, indent_direction='none')
     np.testing.assert_almost_equal(contour, 1j*np.linspace(1e-4, 1e2, 100))
+    assert len(record) == 2
+    assert re.search("encirclements .* non-integer", str(record[0].message))
+    assert re.search("encirclements does not match", str(record[1].message))
 
     # Nyquist plot with poles at the origin, omega unspecified
     sys = ct.tf([1], [1, 3, 2]) * ct.tf([1], [1, 0])
@@ -264,14 +273,19 @@ def test_nyquist_indent_default(indentsys):
 def test_nyquist_indent_dont(indentsys):
     # first value of default omega vector was 0.1, replaced by 0. for contour
     # indent_radius is larger than 0.1 -> no extra quater circle around origin
-    with pytest.warns(UserWarning, match="encirclements does not match"):
+    with pytest.warns() as record:
         count, contour = ct.nyquist_response(
             indentsys, omega=[0, 0.2, 0.3, 0.4], indent_radius=.1007,
             plot=False, return_contour=True)
     np.testing.assert_allclose(contour[0], .1007+0.j)
     # second value of omega_vector is larger than indent_radius: not indented
     assert np.all(contour.real[2:] == 0.)
 
+    # Make sure warnings are as expected
+    assert len(record) == 2
+    assert re.search("encirclements .* non-integer", str(record[0].message))
+    assert re.search("encirclements does not match", str(record[1].message))
+
 
 def test_nyquist_indent_do(indentsys):
     plt.figure();
@@ -352,9 +366,8 @@ def test_nyquist_exceptions():
         ct.nyquist_plot(sys, indent_direction='up')
 
     # Discrete time system sampled above Nyquist frequency
-    sys = ct.drss(2, 1, 1)
-    sys.dt = 0.01
-    with pytest.warns(UserWarning, match="above Nyquist"):
+    sys = ct.ss([[-0.5, 0], [1, 0.5]], [[0], [1]], [[1, 0]], 0, 0.1)
+    with pytest.warns(UserWarning, match="evaluation above Nyquist"):
         ct.nyquist_plot(sys, np.logspace(-2, 3))
 
 

diff --git a/control/tests/xferfcn_test.py b/control/tests/xferfcn_test.py
@@ -3,18 +3,19 @@
 RMM, 30 Mar 2011 (based on TestXferFcn from v0.4a)
 """
 
+import operator
+import re
+
 import numpy as np
 import pytest
-import operator
 
 import control as ct
-from control import StateSpace, TransferFunction, rss, evalfr
-from control import ss, ss2tf, tf, tf2ss, zpk
-from control import isctime, isdtime, sample_system
-from control import defaults, reset_defaults, set_defaults
+from control import (StateSpace, TransferFunction, defaults, evalfr, isctime,
+                     isdtime, reset_defaults, rss, sample_system, set_defaults,
+                     ss, ss2tf, tf, tf2ss, zpk)
 from control.statesp import _convert_to_statespace
-from control.xferfcn import _convert_to_transfer_function
 from control.tests.conftest import slycotonly
+from control.xferfcn import _convert_to_transfer_function
 
 
 class TestXferFcn:
@@ -836,9 +837,14 @@ def test_dcgain_discr(self):
 
         # differencer, with warning
         sys = TransferFunction(1, [1, -1], True)
-        with pytest.warns(RuntimeWarning, match="divide by zero"):
+        with pytest.warns() as record:
             np.testing.assert_equal(
                 sys.dcgain(warn_infinite=True), np.inf)
+        assert len(record) == 2     # generates two RuntimeWarnings
+        assert record[0].category is RuntimeWarning
+        assert re.search("divide by zero", str(record[0].message))
+        assert record[1].category is RuntimeWarning
+        assert re.search("invalid value", str(record[1].message))
 
         # summer
         sys = TransferFunction([1, -1], [1], True)