diff --git a/core/tests/test_auth_backend.py b/core/tests/test_auth_backend.py
new file mode 100644
index 00000000..97eaac1b
--- /dev/null
+++ b/core/tests/test_auth_backend.py
@@ -0,0 +1,27 @@
+import pytest
+from django.contrib.auth.models import Permission
+from model_bakery import baker
+
+from core.models import Group, User
+
+
+@pytest.mark.django_db
+def test_with_perm():
+    """Test that `SithModelBackend.with_perm` works as intended."""
+    perms = baker.make(Permission, _quantity=4)
+    groups = baker.make(Group, _quantity=2)
+    groups[0].permissions.set(perms[0:2])
+    groups[1].permissions.set(perms[2:4])
+    users = [
+        baker.make(User),
+        baker.make(User, groups=[groups[0]]),
+        baker.make(User, groups=[groups[1]]),
+        baker.make(User, user_permissions=[perms[0]]),
+        baker.make(User, user_permissions=[perms[2]]),
+        baker.make(User, groups=[groups[1]], user_permissions=[perms[0]]),
+    ]
+
+    expected = [users[1], users[3], users[5]]
+    assert list(User.objects.with_perm(perms[0])) == expected
+    str_repr = f"{perms[0].content_type.app_label}.{perms[0].codename}"
+    assert list(User.objects.with_perm(str_repr)) == expected
diff --git a/counter/tests/test_counter.py b/counter/tests/test_counter.py
index 581b5b07..83b65021 100644
--- a/counter/tests/test_counter.py
+++ b/counter/tests/test_counter.py
@@ -108,6 +108,13 @@ class TestFullClickBase(TestCase):
 
 
 class TestRefilling(TestFullClickBase):
+    @classmethod
+    def setUpTestData(cls):
+        super().setUpTestData()
+        cls.board_admin.user_permissions.add(
+            Permission.objects.get(codename="add_refilling")
+        )
+
     def login_in_bar(self, barmen: User | None = None):
         used_barman = barmen if barmen is not None else self.board_admin
         self.client.post(
@@ -147,7 +154,7 @@ class TestRefilling(TestFullClickBase):
         assert self.updated_amount(self.customer) == 0
 
     def test_refilling_no_refer_fail(self):
-        """Check that the refill fails is the HTTP_REFERER header is missing"""
+        """Check that the refill fails if the HTTP_REFERER header is missing"""
 
         def refill():
             return self.client.post(