test: add tests for add_heading_anchors template filter

10 test cases covering: h2/h3/h4 processing, h1/h5 exclusion,
duplicate-slug deduplication, existing-id passthrough, nested HTML
stripping, non-heading passthrough, empty string, empty text, and
anchor placement inside the heading element.

Author: nagasrisai

apps/pages/tests/test_templatetags.py

@@ -0,0 +1,77 @@
+"""Tests for apps/pages/templatetags/page_tags.py."""
+
+from django.test import SimpleTestCase
+
+from apps.pages.templatetags.page_tags import add_heading_anchors
+
+
+class AddHeadingAnchorsFilterTests(SimpleTestCase):
+    """Tests for the ``add_heading_anchors`` template filter."""
+
+    def test_h2_gets_id_and_anchor_link(self):
+        """An h2 heading receives an id attribute and a pilcrow anchor link."""
+        html = "<h2>2023</h2>"
+        result = add_heading_anchors(html)
+        self.assertIn('id="2023"', result)
+        self.assertIn('href="#2023"', result)
+        self.assertIn("¶", result)
+
+    def test_h3_and_h4_also_processed(self):
+        """h3 and h4 headings are also processed."""
+        for tag in ("h3", "h4"):
+            html = f"<{tag}>Section Title</{tag}>"
+            result = add_heading_anchors(html)
+            self.assertIn('id="section-title"', result)
+            self.assertIn('href="#section-title"', result)
+
+    def test_h1_and_h5_are_not_changed(self):
+        """h1 and h5 headings are left untouched."""
+        for tag in ("h1", "h5"):
+            html = f"<{tag}>Title</{tag}>"
+            result = add_heading_anchors(html)
+            self.assertNotIn("id=", result)
+            self.assertNotIn("href=", result)
+
+    def test_duplicate_headings_get_unique_ids(self):
+        """Duplicate heading text produces unique, numbered ids."""
+        html = "<h2>Board Resolution</h2><h2>Board Resolution</h2>"
+        result = add_heading_anchors(html)
+        self.assertIn('id="board-resolution"', result)
+        self.assertIn('id="board-resolution-2"', result)
+
+    def test_heading_with_existing_id_is_unchanged(self):
+        """A heading that already has an id attribute is left as-is."""
+        html = '<h2 id="custom-id">My Section</h2>'
+        result = add_heading_anchors(html)
+        self.assertIn('id="custom-id"', result)
+        # No extra anchor link should be injected.
+        self.assertNotIn("headerlink", result)
+
+    def test_heading_with_nested_html_tags(self):
+        """Plain text is extracted from headings that contain nested tags."""
+        html = "<h2><em>Nested</em> Heading</h2>"
+        result = add_heading_anchors(html)
+        self.assertIn('id="nested-heading"', result)
+
+    def test_non_heading_html_is_unchanged(self):
+        """Non-heading elements are passed through unmodified."""
+        html = "<p>Some paragraph</p><ul><li>Item</li></ul>"
+        result = add_heading_anchors(html)
+        self.assertEqual(str(result), html)
+
+    def test_empty_string_returns_empty_string(self):
+        """Passing an empty string returns an empty string."""
+        self.assertEqual(str(add_heading_anchors("")), "")
+
+    def test_heading_with_empty_text_is_unchanged(self):
+        """A heading whose text slugifies to an empty string is left alone."""
+        html = "<h2>  </h2>"
+        result = add_heading_anchors(html)
+        self.assertNotIn("id=", result)
+
+    def test_anchor_link_is_inside_heading(self):
+        """The pilcrow anchor link appears inside the heading element."""
+        html = "<h2>Resolutions 2022</h2>"
+        result = str(add_heading_anchors(html))
+        # The closing </h2> must come after the anchor link.
+        self.assertIn("¶</a></h2>", result)