Add regression test for Node256 fixupMaxVersion

test_conflict_set.py

@@ -223,6 +223,9 @@ def test_merge_child_node48():
 
 
 def test_fixup_256():
+    # All children are written at the same version, so this test passes even
+    # if fixupMaxVersion only considers some of them. See
+    # test_fixup_256_heterogeneous_versions for that case.
     with DebugConflictSet() as cs:
         cs.addWrites(0, write(bytes([1])))
         for i in range(256):
@@ -231,6 +234,20 @@ def test_fixup_256():
         cs.check(read(0, bytes([1]), bytes([2])))
 
 
+def test_fixup_256_heterogeneous_versions():
+    # Regression test for issue #89: recomputing the maxVersion of a Node256
+    # must consider all of its children, not just those with an index < 16.
+    # Here the highest-version child ("\x10\x50") has an index >= 16, and the
+    # range write ends at the Node256, which erases that child from the range
+    # and recomputes the Node256's maxVersion.
+    with DebugConflictSet() as cs:
+        for i in range(256):
+            cs.addWrites(1, write(bytes([0x10, i])))
+        cs.addWrites(10, write(bytes([0x10, 0x50])))
+        cs.addWrites(11, write(bytes([0x05]), bytes([0x10])))
+        assert cs.check(read(5, bytes([0x10, 0x50]))) == [Result.CONFLICT]
+
+
 def test_large_removal_buffer():
     with DebugConflictSet() as cs:
         for i in range(1000):