use classmethod to build fields on records

test/test_db.py

@@ -43,16 +43,29 @@ def test_crud(db):
 
 def test_pointers(db):
     user = examples.User(name="john", email="john@foo")
-    players = examples.Group(name="players", users=[user])
+    players = examples.Group(name="players", members=[user], groups=[])
 
     with pytest.raises(PointerReferenceError):
         players = db.save(players)
 
     user = db.save(user)
 
-    players.users[0] = user
+    players.members[0] = user
     players = db.save(players)
-    assert players.users[0] == user
+    assert players.members[0] == user
+
+
+def test_subgroups(db):
+    kirk = db.save(examples.User(name="James T. Kirk", email="riskybiznez@starfleet"))
+    pike = db.save(examples.User(name="Christopher Pike", email="hitit@starfleet"))
+
+    tos = db.save(examples.Group(name="The Original Series", members=[kirk]))
+    snw = db.save(examples.Group(name="Strange New Worlds", members=[pike]))
+
+    starfleet = db.save(examples.Group(name="Starfleet", groups=[tos, snw]))
+    assert tos in starfleet.groups
+    assert snw in starfleet.groups
+    assert kirk in set([user for group in starfleet.groups for user in group.members])
 
 
 def test_unique(db):