Move '_scalar_property' to '_helpers'.

Also, add explicit coverage for it.

gcloud/storage/_helpers.py

@@ -168,3 +168,17 @@ def __exit__(self, type, value, traceback):
         if type is None:
             if self._deferred:
                 self._wrapped._patch_properties(self._deferred)
+
+
+def _scalar_property(fieldname):
+    """Create a property descriptor around the :class:`_PropertyMixin` helpers.
+    """
+    def _getter(self):
+        """Scalar property getter."""
+        return self.properties[fieldname]
+
+    def _setter(self, value):
+        """Scalar property setter."""
+        self._patch_properties({fieldname: value})
+
+    return property(_getter, _setter)

gcloud/storage/key.py

@@ -6,25 +6,12 @@
 from StringIO import StringIO
 
 from gcloud.storage._helpers import _PropertyMixin
+from gcloud.storage._helpers import _scalar_property
 from gcloud.storage.acl import ObjectACL
 from gcloud.storage.exceptions import StorageError
 from gcloud.storage.iterator import Iterator
 
 
-def _scalar_property(fieldname):
-    """Create a property descriptor around the :class:`_PropertyMixin` helpers.
-    """
-    def _getter(self):
-        """Scalar property getter."""
-        return self.properties[fieldname]
-
-    def _setter(self, value):
-        """Scalar property setter."""
-        self._patch_properties({fieldname: value})
-
-    return property(_getter, _setter)
-
-
 class Key(_PropertyMixin):
     """A wrapper around Cloud Storage's concept of an ``Object``."""
 

gcloud/storage/test__helpers.py

@@ -214,6 +214,34 @@ def test___exit___no_error_aggregates__patch_properties(self):
         self.assertEqual(kw[0]['query_params'], {'projection': 'full'})
 
 
+class Test__scalar_property(unittest2.TestCase):
+
+    def _callFUT(self, fieldName):
+        from gcloud.storage._helpers import _scalar_property
+        return _scalar_property(fieldName)
+
+    def test_getter(self):
+
+        class Test(object):
+            def __init__(self, **kw):
+                self.properties = kw.copy()
+            do_re_mi = self._callFUT('solfege')
+
+        test = Test(solfege='Latido')
+        self.assertEqual(test.do_re_mi, 'Latido')
+
+    def test_setter(self):
+
+        class Test(object):
+            def _patch_properties(self, mapping):
+                self._patched = mapping.copy()
+            do_re_mi = self._callFUT('solfege')
+
+        test = Test()
+        test.do_re_mi = 'Latido'
+        self.assertEqual(test._patched, {'solfege': 'Latido'})
+
+
 class _Connection(object):
 
     def __init__(self, *responses):