Modify tests per balance constraint (#161)

gittip/billing/payday.py

@@ -264,7 +264,7 @@ def transfer(self, tipper, tippee, amount):
 
             try:
                 self.debit_participant(cursor, tipper, amount)
-            except ValueError:
+            except IntegrityError:
                 return False
 
             self.credit_participant(cursor, tippee, amount)
@@ -288,13 +288,13 @@ def debit_participant(self, cursor, participant, amount):
         RETURNING balance
 
         """
+
+        # This will fail with IntegrityError if the balanced goes below zero.
+        # We catch that and return false in our caller.
         cursor.execute(DECREMENT, (amount, participant))
+
         rec = cursor.fetchone()
         assert rec is not None, (amount, participant)  # sanity check
-        if rec['balance'] < 0:
-            # User is out of money. Bail. The transaction will be rolled back
-            # by our context manager.
-            raise ValueError()  # TODO: proper exception type
 
 
     def credit_participant(self, cursor, participant, amount):

tests/test_billing.py

@@ -18,7 +18,7 @@ def setUp(self):
         super(TestCard, self).setUp()
         self.balanced_account_uri = '/v1/marketplaces/M123/accounts/A123'
         self.stripe_customer_id = 'deadbeef'
-        
+
     @mock.patch('balanced.Account')
     def test_balanced_card(self, ba):
         card = mock.Mock()
@@ -702,7 +702,7 @@ def get_balance_amount(participant):
         with self.db.get_connection() as conn:
             cur = conn.cursor()
 
-            with self.assertRaises(ValueError):
+            with self.assertRaises(IntegrityError):
                 self.payday.debit_participant(cur, participant, amount)
 
     def test_credit_participant(self):