Add new unit test for SpanSet intersection

tests/test_spanSets.py

@@ -252,6 +252,20 @@ def testIntersection(self):
         for expected, val in zip(expectedYRange, spanSetIntersectMask):
             self.assertEqual(expected, val.getY())
 
+    def testIntersectionWithGap(self):
+        # This test was created in DM-47945 to fix a bug where the
+        # intersection of two spansets where multiple spans have the same
+        # y-value would fail.
+        spans1 = afwGeom.SpanSet([afwGeom.Span(1, 0, 3), afwGeom.Span(1, 5, 7)])
+        spans2 = afwGeom.SpanSet([afwGeom.Span(1, 2, 6)])
+        intersection = spans1.intersect(spans2)
+        trueIntersection = afwGeom.SpanSet([afwGeom.Span(1, 2, 3), afwGeom.Span(1, 5, 6)])
+
+        self.assertEqual(len(intersection), 2)
+
+        for a, b in zip(intersection, trueIntersection):
+            self.assertEqual(a, b)
+
     def testIntersectNot(self):
         firstSpanSet, secondSpanSet = self.makeOverlapSpanSets()