.

wcfs/internal/xbtree.py

@@ -216,6 +216,9 @@ def StructureOf(znode):
 
 # Restructure reorganizes ZODB BTree instance (not Tree) according to specified
 # topology structure.
+#
+# NOTE ZODB BTree package does not tolerate structures with empty BTree nodes
+# except for the single case of empty tree.
 def Restructure(ztree, newStructure):
     _ = _zclassify(ztree)
     assert _.is_ztree

wcfs/internal/xbtree_test.py

@@ -344,8 +344,23 @@ def test_allStructs():
                                # T4/
                                #    nothing - rightmost bucket is always empty
                               ]
+
     # XXX Y tests for maxsplit=2 / maxdepth=2 ?
     # (if yes -> compare with set, not exact order, and use topoencoding on the right)
+    def TY(keys, maxdepth, maxsplit):
+        yv = Y(keys, maxdepth, maxsplit)
+        return list([xbtree.TopoEncode(_) for _ in yv])
+
+    assert TY([1,3], 1, 1) == [
+                                'T/B1,3',
+                                'T/T/B1,3',
+                                'T/T2/B1-B3',
+                                'T/T3/B1-B3',
+                                'T2/B1-B3',
+                                'T2/T-T/B1-B3',
+                                'T3/B1-B3',
+                                'T3/T-T/B1-B3',
+                              ]
 
 
 # XBlk simulates ZBlk without xbtree_test.py depending on file_zodb.py