'Check top-level invoice information in the latest history record.'

def _assert_history_invoice_info(self, is_valid=True, customer_ref=None, internal_ref=None):

    latest = self._latest_history()
    self.assertEqual(latest['is_valid'], is_valid)
    self.assertEqual(latest['customer_reference'], customer_ref)
    self.assertEqual(latest['internal_reference'], internal_ref)
