Add unit test.

see #879

modoboa/admin/tests/test_dnsbl.py

@@ -0,0 +1,27 @@
+"""DNSBL related tests."""
+
+from django.core import management
+from django.test import override_settings
+
+from modoboa.lib.tests import ModoTestCase
+
+from .. import factories
+from .. import models
+
+
+class DNSBLTestCase(ModoTestCase):
+    """TestCase for DNSBL related features."""
+
+    @classmethod
+    def setUpTestData(cls):
+        """Create some data."""
+        super(DNSBLTestCase, cls).setUpTestData()
+        factories.DomainFactory(name="modoboa.org")
+
+    @override_settings(DNSBL_PROVIDERS=["zen.spamhaus.org"])
+    def test_management_command(self):
+        """Check that command works fine."""
+        management.call_command("modo", "check_dnsbl")
+        self.assertTrue(
+            models.DNSBLResult.objects.filter(
+                domain__name="modoboa.org").exists())