TST: Added a unit test to avoid CI problems

madphysicist · madphysicist · commit 0b91d8ec999d · 2024-07-24T17:31:02.000-05:00
diff --git a/lib/matplotlib/tests/test_transforms.py b/lib/matplotlib/tests/test_transforms.py
@@ -341,6 +341,31 @@ def test_deepcopy(self):
         assert_array_equal(s.get_matrix(), a.get_matrix())
 
 
+class TestAffineDeltaTransform:
+    def test_invalidate(self):
+        before = np.array([[1.0, 4.0, 0.0],
+                           [5.0, 1.0, 0.0],
+                           [0.0, 0.0, 1.0]])
+        after = np.array([[1.0, 3.0, 0.0],
+                          [5.0, 1.0, 0.0],
+                          [0.0, 0.0, 1.0]])
+
+        # Translation and skew present
+        base = mtransforms.Affine2D.from_values(1, 5, 4, 1, 2, 3)
+        t = mtransforms.AffineDeltaTransform(base)
+        assert_array_equal(t.get_matrix(), before)
+
+        # Mess with the internal structure of `base` without invalidating
+        # This should not affect this transform because it's a passthrough:
+        # it's always invalid
+        base.get_matrix()[0, 1:] = 3
+        assert_array_equal(t.get_matrix(), after)
+
+        # Invalidate the base
+        base.invalidate()
+        assert_array_equal(t.get_matrix(), after)
+
+
 def test_non_affine_caching():
     class AssertingNonAffineTransform(mtransforms.Transform):
         """
