Improve test coverage

python/mwmatching.py

@@ -671,12 +671,11 @@ class _MatchingContext:
             return
 
         # Update the priority of "y" in its UnionFindQueue.
-        prev_min = by.vertex_set.min_prio()
         self.vertex_set_node[y].set_prio(prio)
 
         # If the blossom is unlabeled and the new edge becomes its least-slack
         # S-edge, insert or update the blossom in the global delta2 queue.
-        if (by.label == _LABEL_NONE) and (prio < prev_min):
+        if by.label == _LABEL_NONE:
             prio += by.vertex_dual_offset
             if by.delta2_node is None:
                 by.delta2_node = self.delta2_queue.insert(prio, by)
@@ -1067,7 +1066,7 @@ class _MatchingContext:
 
         if blossom.label == _LABEL_S:
             self.remove_blossom_label_s(blossom)
-        elif blossom.label == _LABEL_T:
+        else:
             self.remove_blossom_label_t(blossom)
 
     def _check_alternating_tree_consistency(self) -> None:

python/test_mwmatching.py

@@ -243,6 +243,23 @@ class TestMaximumWeightMatching(unittest.TestCase):
             mwm([(1,2,19), (1,4,17), (1,5,19), (2,3,15), (2,5,21), (4,6,18), (4,7,11), (5,6,19)]),
             [(1,5), (2,3), (4,6)])
 
+    def test52_augment_blossom_nested2(self):
+        """augment nested blossoms"""
+        #
+        #   [4]--15     19--[2]
+        #    |     \   /     |
+        #   16      [1]     21
+        #    |     /   \     |
+        #   [5]--17     19--[3]
+        #    |
+        #   10
+        #    |
+        #   [6]
+        #
+        self.assertEqual(
+            mwm([(1,2,19), (1,3,19), (1,4,15), (1,5,17), (2,3,21), (4,5,16), (5,6,10)]),
+            [(1,4), (2,3), (5,6)])
+
     def test61_triangles_n9(self):
         """t.f 9 nodes"""
         #