Ensure static segments don't have one extra user

src/wagtail_personalisation/forms.py

@@ -116,7 +116,7 @@ class SegmentAdminForm(WagtailAdminModelForm):
                 passes = adapter._test_rules(instance.get_rules(), request, instance.match_any)
                 if passes:
                     matched_count += 1
-                    if instance.count == 0 or len(users_to_add) <= instance.count:
+                    if instance.count == 0 or len(users_to_add) < instance.count:
                         if instance.randomise_into_segment():
                             users_to_add.append(user)
                         else:

tests/unit/test_static_dynamic_segments.py

@@ -45,6 +45,20 @@ def test_user_added_to_static_segment_at_creation(site, user, mocker):
     assert user in instance.static_users.all()
 
 
+@pytest.mark.django_db
+def test_user_not_added_to_full_static_segment_at_creation(site, django_user_model, mocker):
+    django_user_model.objects.create(username='first')
+    django_user_model.objects.create(username='second')
+    segment = SegmentFactory.build(type=Segment.TYPE_STATIC, count=1)
+    rule = VisitCountRule(counted_page=site.root_page)
+    form = form_with_data(segment, rule)
+    mocker.patch('wagtail_personalisation.rules.VisitCountRule.test_user',
+                 side_effect=[True, True])
+    instance = form.save()
+
+    assert len(instance.static_users.all()) == 1
+
+
 @pytest.mark.django_db
 def test_anonymous_user_not_added_to_static_segment_at_creation(site, client, mocker):
     session = client.session