Feature/alias elements

rwslib/builders/metadata.py

@@ -461,7 +461,7 @@ def __init__(self, oid, order_number=None, mandatory=False):
     def build(self, builder):
         """Build XML by appending to builder"""
         params = dict(StudyEventOID=self.oid, Mandatory=bool_to_yes_no(self.mandatory))
-        if self._order_number:
+        if self._order_number is not None:
             params["OrderNumber"] = self._order_number
         builder.start("StudyEventRef", params)
         builder.end("StudyEventRef")

rwslib/tests/test_builders_metadata.py

@@ -151,6 +151,12 @@ def test_optional_order_number(self):
         self.assertIsNone(doc.get('OrderNumber'))
         self.assertEquals("No", doc.get('Mandatory'))
 
+    def test_zero_order_number(self):
+        """Not that it's entirely sensible, but it's cleaner"""
+        ser = StudyEventRef("OID", order_number=0)
+        doc = obj_to_doc(ser)
+        self.assertEquals("0", str(doc.get('OrderNumber')))
+
     def test_mandatory_study_event_ref(self):
         ser = StudyEventRef("OID", mandatory=True)
         doc = obj_to_doc(ser)