fix test for purchase order
diff --git a/erpnext/controllers/recurring_document.py b/erpnext/controllers/recurring_document.py
index 7b4310b..32b1ceb 100644
--- a/erpnext/controllers/recurring_document.py
+++ b/erpnext/controllers/recurring_document.py
@@ -16,6 +16,8 @@
 def create_recurring_documents():
 	manage_recurring_documents("Sales Order")
 	manage_recurring_documents("Sales Invoice")
+	manage_recurring_documents("Purchase Order")
+	manage_recurring_documents("Purchase Invoice")
 
 def manage_recurring_documents(doctype, next_date=None, commit=True):
 	"""
@@ -28,6 +30,10 @@
 		date_field = "transaction_date"
 	elif doctype == "Sales Invoice":
 		date_field = "posting_date"
+	elif doctype == "Purchase Order":
+		date_field = "transaction_date"
+	elif doctype == "Purchase Invoice":
+		date_field = "posting_date"
 
 	recurring_documents = frappe.db.sql("""select name, recurring_id
 		from `tab{}` where ifnull(is_recurring, 0)=1