diff -r baed516c6f6e -r e4f11ef1face cubicweb/test/data/schema.py
--- a/cubicweb/test/data/schema.py	Fri Jun 10 16:45:20 2016 +0200
+++ b/cubicweb/test/data/schema.py	Thu Jun 16 15:53:01 2016 +0200
@@ -17,7 +17,7 @@
 # with CubicWeb.  If not, see <http://www.gnu.org/licenses/>.
 
 from yams.buildobjs import (EntityType, String, RichString, Bytes,
-                            SubjectRelation, RelationDefinition)
+                            ComputedRelation, SubjectRelation, RelationDefinition)
 
 from cubicweb.schema import (WorkflowableEntityType,
                              RQLConstraint, RQLVocabularyConstraint)
@@ -26,6 +26,10 @@
 from cubicweb import _
 
 
+class buddies(ComputedRelation):
+    rule = 'S in_group G, O in_group G'
+
+
 class Personne(EntityType):
     nom = String(required=True)
     prenom = String()