Fixed bug in update_rates command and added tests

djmoney_rates/management/commands/update_rates.py

@@ -12,9 +12,9 @@ class Command(BaseCommand):
     def handle(self, *args, **options):
         if args:
             try:
-                backend_class = import_from_string(args, "")
+                backend_class = import_from_string(args[0], "")
             except ImportError:
-                raise CommandError("Cannot find custom backend %s. Is it correct" % args)
+                raise CommandError("Cannot find custom backend %s. Is it correct" % args[0])
         else:
             backend_class = money_rates_settings.DEFAULT_BACKEND
 

tests/test_commands.py

@@ -0,0 +1,29 @@
+from __future__ import unicode_literals
+
+import unittest
+
+from django.core.management import call_command
+from django.core.management.base import CommandError
+
+from djmoney_rates.backends import BaseRateBackend
+from djmoney_rates.models import Rate, RateSource
+
+
+class CustomBackend(BaseRateBackend):
+    source_name = "custom-backend"
+    base_currency = "USD"
+
+    def get_rates(self):
+        return {"PLN": 3.07, "EUR": 0.74}
+
+
+class TestCommands(unittest.TestCase):
+    def test_fail_when_custom_backend_do_not_exists(self):
+        with self.assertRaises(CommandError):
+            call_command("update_rates", "fake.custom.Backend")
+
+    def test_custom_backend_used_when_specified(self):
+        call_command("update_rates", "tests.test_commands.CustomBackend")
+
+        self.assertEqual(1, RateSource.objects.filter(name="custom-backend").count())
+        self.assertEqual(2, Rate.objects.filter(source__name="custom-backend").count())