pythoningLearning
diff --git a/‎opc/package.py‎
Lines changed: 5 additions & 0 deletions b/‎opc/package.py‎
Lines changed: 5 additions & 0 deletions
diff --git a/‎tests/test_package.py‎
Lines changed: 10 additions & 1 deletion b/‎tests/test_package.py‎
Lines changed: 10 additions & 1 deletion
@@ -105,6 +105,11 @@ class RelationshipCollection(object):
     """
     def __init__(self, baseURI):
         super(RelationshipCollection, self).__init__()
+        self._rels = []
+
+    def __len__(self):
+        """Implements len() built-in on this object"""
+        return self._rels.__len__()
 
 
 class Unmarshaller(object):
 
@@ -13,7 +13,9 @@
 
 from mock import call, Mock
 
-from opc.package import OpcPackage, Part, PartFactory, Unmarshaller
+from opc.package import (
+    OpcPackage, Part, PartFactory, RelationshipCollection, Unmarshaller
+)
 from opc.packuri import PACKAGE_URI
 
 from .unitutil import class_mock, method_mock
@@ -94,6 +96,13 @@ def it_constructs_a_part_instance(self, Part_):
         assert part == Part_.return_value
 
 
+class DescribeRelationshipCollection(object):
+
+    def it_has_a_len(self):
+        rels = RelationshipCollection(None)
+        assert len(rels) == 0
+
+
 class DescribeUnmarshaller(object):
 
     @pytest.fixture