diff -r 0095961df66c -r de62952550d9 web/test/data/schema.py
--- a/web/test/data/schema.py	Wed Jan 28 11:59:06 2015 +0100
+++ b/web/test/data/schema.py	Thu Jan 29 16:40:08 2015 +0100
@@ -95,3 +95,8 @@
 
 # used by windmill for `test_edit_relation`
 from cubes.folder.schema import Folder
+
+
+class TreeNode(EntityType):
+    name = String(required=True)
+    parent = SubjectRelation('TreeNode', cardinality='?*')