pythoningLearning
diff --git a/‎opc/package.py‎
Lines changed: 15 additions & 0 deletions b/‎opc/package.py‎
Lines changed: 15 additions & 0 deletions
diff --git a/‎tests/test_package.py‎
Lines changed: 9 additions & 1 deletion b/‎tests/test_package.py‎
Lines changed: 9 additions & 1 deletion
@@ -36,6 +36,14 @@ def open(pkg_file):
         Unmarshaller.unmarshal(pkg_reader, pkg, PartFactory)
         return pkg
 
+    @property
+    def parts(self):
+        """
+        Return an immutable sequence (tuple) containing a reference to each
+        of the parts in this package.
+        """
+        return tuple([p for p in self._walk_parts(self._rels)])
+
     @property
     def rels(self):
         """
@@ -52,6 +60,13 @@ def _add_relationship(self, reltype, target, rId, external=False):
         """
         return self._rels.add_relationship(reltype, target, rId, external)
 
+    @staticmethod
+    def _walk_parts(rels, visited_parts=None):
+        """
+        Generate exactly one reference to each of the parts in the package by
+        performing a depth-first traversal of the rels graph.
+        """
+
 
 class Part(object):
     """
 
@@ -11,7 +11,7 @@
 
 import pytest
 
-from mock import call, Mock
+from mock import call, Mock, patch
 
 from opc.package import (
     OpcPackage, Part, PartFactory, _Relationship, RelationshipCollection,
@@ -73,6 +73,14 @@ def it_can_add_a_relationship_to_a_part(self):
         pkg._rels.add_relationship.assert_called_once_with(reltype, target,
                                                            rId, False)
 
+    def it_has_an_immutable_sequence_containing_its_parts(self):
+        # mockery ----------------------
+        parts = [Mock(name='part1'), Mock(name='part2')]
+        pkg = OpcPackage()
+        # verify -----------------------
+        with patch.object(OpcPackage, '_walk_parts', return_value=parts):
+            assert pkg.parts == (parts[0], parts[1])
+
 
 class DescribePart(object):