[layerindex-web,4/5] tests: add DuplicatesView tests

diff --git a/tests/test_duplicates_view.py b/tests/test_duplicates_view.py
new file mode 100644
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+++ b/tests/test_duplicates_view.py
@@ -0,0 +1,218 @@ 
+# layerindex-web - tests for DuplicatesView
+#
+# Copyright (C) 2026 Tim Orling <tim.orling@konsulko.com>
+#
+# Licensed under the MIT license, see COPYING.MIT for details
+#
+# SPDX-License-Identifier: MIT
+
+# Tests for bug #16175 - Duplicates page timeout
+# https://bugzilla.yoctoproject.org/show_bug.cgi?id=16175
+#
+# The fix replaces Python list comprehensions used to build IN (...) clauses
+# with Django ORM subqueries, and adds select_related to avoid N+1 queries
+# when the template resolves layerbranch__layer names.
+
+import pytest
+from django.test import TestCase
+from django.urls import reverse
+
+from layerindex.models import (Branch, LayerItem, LayerBranch, Recipe,
+                                BBClass, IncFile)
+
+
+@pytest.mark.django_db
+class TestDuplicatesView(TestCase):
+    """Tests for DuplicatesView (bug #16175 - duplicates page timeout fix)."""
+
+    def setUp(self):
+        self.branch = Branch.objects.create(
+            name='main',
+            bitbake_branch='master',
+            short_description='Main branch',
+            sort_priority=1,
+            hidden=False,
+            updates_enabled=True,
+        )
+
+        # Two layers — objects in both will appear as duplicates
+        self.layer_a = LayerItem.objects.create(
+            name='meta-alpha',
+            status='P',
+            layer_type='A',
+            summary='Alpha layer',
+            description='Alpha test layer',
+            vcs_url='git://example.com/meta-alpha.git',
+        )
+        self.layer_b = LayerItem.objects.create(
+            name='meta-beta',
+            status='P',
+            layer_type='S',
+            summary='Beta layer',
+            description='Beta test layer',
+            vcs_url='git://example.com/meta-beta.git',
+        )
+        # A third layer whose objects are unique (should NOT appear as duplicates)
+        self.layer_c = LayerItem.objects.create(
+            name='meta-gamma',
+            status='P',
+            layer_type='S',
+            summary='Gamma layer',
+            description='Gamma test layer',
+            vcs_url='git://example.com/meta-gamma.git',
+        )
+
+        self.lb_a = LayerBranch.objects.create(layer=self.layer_a, branch=self.branch)
+        self.lb_b = LayerBranch.objects.create(layer=self.layer_b, branch=self.branch)
+        self.lb_c = LayerBranch.objects.create(layer=self.layer_c, branch=self.branch)
+
+        # Duplicate recipe (same pn in layer_a and layer_b)
+        Recipe.objects.create(layerbranch=self.lb_a, filename='shared_1.0.bb',
+                               pn='shared', pv='1.0', filepath='recipes-test')
+        Recipe.objects.create(layerbranch=self.lb_b, filename='shared_1.0.bb',
+                               pn='shared', pv='1.0', filepath='recipes-test')
+        # Unique recipe (only in layer_c — should NOT appear)
+        Recipe.objects.create(layerbranch=self.lb_c, filename='unique_1.0.bb',
+                               pn='unique', pv='1.0', filepath='recipes-test')
+
+        # Duplicate class (same name in layer_a and layer_b)
+        BBClass.objects.create(layerbranch=self.lb_a, name='sharedclass')
+        BBClass.objects.create(layerbranch=self.lb_b, name='sharedclass')
+        # Unique class (only in layer_c — should NOT appear)
+        BBClass.objects.create(layerbranch=self.lb_c, name='uniqueclass')
+
+        # Duplicate include file (same path in layer_a and layer_b)
+        IncFile.objects.create(layerbranch=self.lb_a, path='conf/shared.inc')
+        IncFile.objects.create(layerbranch=self.lb_b, path='conf/shared.inc')
+        # Unique include file (only in layer_c — should NOT appear)
+        IncFile.objects.create(layerbranch=self.lb_c, path='conf/unique.inc')
+
+    def _url(self, branch='main'):
+        return reverse('duplicates', kwargs={'branch': branch})
+
+    def test_duplicates_view_returns_200(self):
+        """DuplicatesView should return HTTP 200."""
+        response = self.client.get(self._url())
+        self.assertEqual(response.status_code, 200)
+
+    # --- Recipes ---
+
+    def test_duplicate_recipes_included(self):
+        """Recipes appearing in more than one layer should be in context."""
+        response = self.client.get(self._url())
+        pns = [r.pn for r in response.context['recipes']]
+        self.assertIn('shared', pns)
+
+    def test_unique_recipes_excluded(self):
+        """Recipes appearing in only one layer should not appear."""
+        response = self.client.get(self._url())
+        pns = [r.pn for r in response.context['recipes']]
+        self.assertNotIn('unique', pns)
+
+    def test_duplicate_recipes_have_two_rows(self):
+        """Each layer's entry for the duplicate recipe should be present."""
+        response = self.client.get(self._url())
+        shared = [r for r in response.context['recipes'] if r.pn == 'shared']
+        self.assertEqual(len(shared), 2)
+
+    # --- Classes ---
+
+    def test_duplicate_classes_included(self):
+        """Classes appearing in more than one layer should be in context."""
+        response = self.client.get(self._url())
+        names = [c.name for c in response.context['classes']]
+        self.assertIn('sharedclass', names)
+
+    def test_unique_classes_excluded(self):
+        """Classes appearing in only one layer should not appear."""
+        response = self.client.get(self._url())
+        names = [c.name for c in response.context['classes']]
+        self.assertNotIn('uniqueclass', names)
+
+    def test_duplicate_classes_have_two_rows(self):
+        """Both layer entries for the duplicate class should be present."""
+        response = self.client.get(self._url())
+        shared = [c for c in response.context['classes'] if c.name == 'sharedclass']
+        self.assertEqual(len(shared), 2)
+
+    # --- Include files ---
+
+    def test_duplicate_incfiles_included(self):
+        """Include files appearing in more than one layer should be in context."""
+        response = self.client.get(self._url())
+        paths = [f.path for f in response.context['incfiles']]
+        self.assertIn('conf/shared.inc', paths)
+
+    def test_unique_incfiles_excluded(self):
+        """Include files appearing in only one layer should not appear."""
+        response = self.client.get(self._url())
+        paths = [f.path for f in response.context['incfiles']]
+        self.assertNotIn('conf/unique.inc', paths)
+
+    def test_duplicate_incfiles_have_two_rows(self):
+        """Both layer entries for the duplicate include file should be present."""
+        response = self.client.get(self._url())
+        shared = [f for f in response.context['incfiles'] if f.path == 'conf/shared.inc']
+        self.assertEqual(len(shared), 2)
+
+    # --- Layer filter ---
+
+    def test_layer_filter_restricts_recipes(self):
+        """Passing ?l=<layer_id> should restrict results to that layer."""
+        response = self.client.get(self._url() + f'?l={self.layer_a.id}')
+        self.assertEqual(response.status_code, 200)
+        # With only one layer selected, nothing can be a duplicate
+        pns = [r.pn for r in response.context['recipes']]
+        self.assertNotIn('shared', pns)
+
+    def test_wrong_branch_returns_empty(self):
+        """A branch with no data should return empty querysets."""
+        other = Branch.objects.create(
+            name='other',
+            bitbake_branch='other',
+            sort_priority=50,
+        )
+        response = self.client.get(reverse('duplicates', kwargs={'branch': 'other'}))
+        self.assertEqual(response.status_code, 200)
+        self.assertEqual(len(list(response.context['recipes'])), 0)
+        self.assertEqual(len(list(response.context['classes'])), 0)
+        self.assertEqual(len(list(response.context['incfiles'])), 0)
+
+    def test_select_related_avoids_extra_queries(self):
+        """Ensure layerbranch and layer are fetched with select_related.
+
+        Checks that accessing layerbranch.layer.name on query results does not
+        trigger additional database queries (i.e. select_related is working).
+        """
+        from django.db import connection, reset_queries
+        from django.conf import settings
+
+        settings.DEBUG = True
+        reset_queries()
+
+        view = __import__('layerindex.views', fromlist=['DuplicatesView']).DuplicatesView
+        v = view()
+        v.kwargs = {'branch': 'main'}
+        v.request = None
+
+        recipes = list(v.get_recipes([]))
+        classes = list(v.get_classes([]))
+        incfiles = list(v.get_incfiles([]))
+
+        # Record query count after fetching
+        query_count_after_fetch = len(connection.queries)
+
+        # Access layerbranch.layer.name on every result — should NOT fire new queries
+        for r in recipes:
+            _ = r.layerbranch.layer.name
+        for c in classes:
+            _ = c.layerbranch.layer.name
+        for f in incfiles:
+            _ = f.layerbranch.layer.name
+
+        query_count_after_access = len(connection.queries)
+        settings.DEBUG = False
+
+        self.assertEqual(query_count_after_fetch, query_count_after_access,
+                         "Unexpected extra queries when accessing layerbranch.layer.name — "
+                         "select_related may not be working")