add skeleton

tests.py

@@ -0,0 +1,29 @@
+from unittest import mock
+
+import services
+from containers import Container
+from dependency_injector.wiring import Provide, inject
+
+
+@inject
+def run(service: services.BusinessLogic = Provide[Container.business_logic]):
+    service.send("test@receiver")
+
+
+def test_is_mail_send():
+    container = Container()
+    container.init_resources()
+    container.wire(modules=[__name__])
+
+    email_service = mock.Mock(services.EmailService)
+    invoice_service = mock.Mock(services.InvoiceService)
+
+    invoice_service.create_invoice.return_value = "test invoice"
+
+    with container.override_providers(
+            email_service=email_service,
+            invoice_service=invoice_service):
+        run()
+
+    email_service.send.assert_called_once_with("test@receiver", "test invoice")
+    invoice_service.create_invoice.assert_called()