Make sure we update the correct month for billing:

When populating the monthly billing records on a schedule, we need
to ensure the correct month is being updated.

As an example, if the current datetime is 31 Mar 2016, 23:00. The
BST equivalent is the 1st April. Therefore we need to ensure we
update billing for April, not March. This takes care of that.

tests/app/db.py

@@ -6,9 +6,13 @@ from app.dao.jobs_dao import dao_create_job
 from app.dao.service_inbound_api_dao import save_service_inbound_api
 from app.models import (
     ApiKey,
+    EMAIL_TYPE,
+    SMS_TYPE,
+    KEY_TYPE_NORMAL,
     Service,
     User,
     Template,
+    MonthlyBilling,
     Notification,
     ScheduledNotification,
     ServicePermission,
@@ -17,10 +21,8 @@ from app.models import (
     InboundSms,
     InboundNumber,
     Organisation,
-    EMAIL_TYPE,
-    SMS_TYPE,
-    KEY_TYPE_NORMAL,
-    ServiceInboundApi)
+    ServiceInboundApi
+)
 from app.dao.users_dao import save_model_user
 from app.dao.notifications_dao import dao_create_notification, dao_created_scheduled_notification
 from app.dao.templates_dao import dao_create_template
@@ -258,7 +260,12 @@ def create_organisation(colour='blue', logo='test_x2.png', name='test_org_1'):
 
 
 def create_rate(start_date, value, notification_type):
-    rate = Rate(id=uuid.uuid4(), valid_from=start_date, rate=value, notification_type=notification_type)
+    rate = Rate(
+        id=uuid.uuid4(),
+        valid_from=start_date,
+        rate=value,
+        notification_type=notification_type
+    )
     db.session.add(rate)
     db.session.commit()
     return rate
@@ -290,3 +297,24 @@ def create_inbound_number(number, provider='mmg', active=True, service_id=None):
     db.session.add(inbound_number)
     db.session.commit()
     return inbound_number
+
+
+def create_monthly_billing_entry(
+    service,
+    start_date,
+    end_date,
+    notification_type,
+    monthly_totals=[]
+):
+    entry = MonthlyBilling(
+        service_id=service.id,
+        notification_type=notification_type,
+        monthly_totals=monthly_totals,
+        start_date=start_date,
+        end_date=end_date
+    )
+
+    db.session.add(entry)
+    db.session.commit()
+
+    return entry