Fixed #132 -- Reverse payment fee calculation

src/tests/testdummy/payment.py

@@ -0,0 +1,19 @@
+import logging
+
+from pretix.base.payment import BasePaymentProvider
+
+logger = logging.getLogger('tests.testdummy.ticketoutput')
+
+
+class DummyPaymentProvider(BasePaymentProvider):
+    identifier = 'testdummy'
+    verbose_name = 'Test dummy'
+
+    def order_pending_render(self, request, order) -> str:
+        pass
+
+    def payment_is_valid_session(self, request) -> bool:
+        pass
+
+    def checkout_confirm_render(self, request) -> str:
+        pass