fix matplotlib tests for Windows 11

Author: Dr-Irv

conftest.py

@@ -0,0 +1,36 @@
+import gc
+
+import pytest
+
+
+@pytest.fixture
+def mpl_cleanup():
+    """
+    Ensure Matplotlib is cleaned up around a test.
+
+    Before a test is run:
+
+    1) Set the backend to "template" to avoid requiring a GUI.
+
+    After a test is run:
+
+    1) Reset units registry
+    2) Reset rc_context
+    3) Close all figures
+
+    See matplotlib/testing/decorators.py#L24.
+    """
+    mpl = pytest.importorskip("matplotlib")
+    mpl_units = pytest.importorskip("matplotlib.units")
+    plt = pytest.importorskip("matplotlib.pyplot")
+    orig_units_registry = mpl_units.registry.copy()
+    try:
+        with mpl.rc_context():
+            mpl.use("template")
+            yield
+    finally:
+        mpl_units.registry.clear()
+        mpl_units.registry.update(orig_units_registry)
+        plt.close("all")
+        # https://matplotlib.org/stable/users/prev_whats_new/whats_new_3.6.0.html#garbage-collection-is-no-longer-run-on-figure-close
+        gc.collect(1)

tests/test_plotting.py

@@ -24,6 +24,11 @@
 )
 
 
+@pytest.fixture(autouse=True)
+def autouse_mpl_cleanup(mpl_cleanup):
+    pass
+
+
 @pytest.fixture
 def close_figures():
     plt.close("all")