Add tests and documentation for anchor-based partial nav inclusion

- Added comprehensive unit tests for anchor parsing, nav extraction,
  unique alias generation, and error handling
- Updated CHANGELOG.md with new feature details for v1.2.0

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: jacobstr

docs/CHANGELOG.md

@@ -1,5 +1,10 @@
 # Changelog
 
+## 1.2.0 (Unreleased)
+
+- Added support for partial nav inclusion using anchor syntax (`!include path/to/mkdocs.yml#SectionName`)
+- Added unique alias generation for anchored includes to prevent naming conflicts
+
 ## 1.1.2
 
 - Dropped official support for Python 3.8

mkdocs_monorepo_plugin/tests/test_plugin.py

@@ -1,8 +1,11 @@
 #!/usr/bin/env python
 
 import unittest
+import os
+import tempfile
 
 from mkdocs_monorepo_plugin import plugin as p
+from mkdocs_monorepo_plugin.parser import IncludeNavLoader
 
 
 class MockServer:
@@ -40,3 +43,90 @@ def test_plugin_on_serve(self):
         server = MockServer()
         plugin.on_serve(server, {})
         self.assertSetEqual(set(server.watched), {"docs"})
+
+
+class TestAnchorBasedPartialNavInclusion(unittest.TestCase):
+    """Tests for anchor-based partial navigation inclusion feature."""
+
+    def setUp(self):
+        """Create a temporary directory with test mkdocs.yml files."""
+        self.test_dir = tempfile.mkdtemp()
+        self.mkdocs_file = os.path.join(self.test_dir, "mkdocs.yml")
+
+        # Create a test mkdocs.yml with multiple nav sections
+        with open(self.mkdocs_file, 'w') as f:
+            f.write("""site_name: TestSite
+docs_dir: docs
+nav:
+  - Home: index.md
+  - Guides:
+    - Getting Started: guides/getting-started.md
+    - Advanced: guides/advanced.md
+  - Reference:
+    - API: reference/api.md
+    - CLI: reference/cli.md
+""")
+
+        # Create docs directory
+        os.makedirs(os.path.join(self.test_dir, "docs"))
+
+    def tearDown(self):
+        """Clean up temporary directory."""
+        import shutil
+        shutil.rmtree(self.test_dir)
+
+    def test_anchor_parsing(self):
+        """Test that anchors are correctly parsed from include paths."""
+        config = {"config_file_path": self.mkdocs_file}
+
+        # Test with anchor
+        loader = IncludeNavLoader(config, "mkdocs.yml#Guides")
+        self.assertEqual(loader.navPath, "mkdocs.yml")
+        self.assertEqual(loader.navSection, "Guides")
+
+        # Test without anchor
+        loader_no_anchor = IncludeNavLoader(config, "mkdocs.yml")
+        self.assertEqual(loader_no_anchor.navPath, "mkdocs.yml")
+        self.assertIsNone(loader_no_anchor.navSection)
+
+    def test_extract_nav_section(self):
+        """Test that specific nav sections can be extracted."""
+        config = {"config_file_path": self.mkdocs_file}
+        loader = IncludeNavLoader(config, "mkdocs.yml#Guides")
+        loader.read()
+
+        # The extracted nav should only contain the Guides section content
+        nav = loader.getNav()
+
+        # Check that we got a list (the content of the Guides section)
+        self.assertIsInstance(nav, list)
+
+        # The nav should contain items from the Guides section
+        self.assertTrue(len(nav) > 0)
+
+    def test_unique_alias_with_section(self):
+        """Test that aliases are unique when sections are specified."""
+        config = {"config_file_path": self.mkdocs_file}
+
+        # Load with section anchor
+        loader_with_section = IncludeNavLoader(config, "mkdocs.yml#Guides")
+        loader_with_section.read()
+        alias_with_section = loader_with_section.getAlias()
+
+        # Load without section anchor
+        loader_without_section = IncludeNavLoader(config, "mkdocs.yml")
+        loader_without_section.read()
+        alias_without_section = loader_without_section.getAlias()
+
+        # Aliases should be different
+        self.assertNotEqual(alias_with_section, alias_without_section)
+        self.assertIn("Guides", alias_with_section)
+
+    def test_section_not_found(self):
+        """Test that an error is raised when the specified section doesn't exist."""
+        config = {"config_file_path": self.mkdocs_file}
+        loader = IncludeNavLoader(config, "mkdocs.yml#NonExistentSection")
+
+        with self.assertRaises(SystemExit):
+            loader.read()
+            loader.getNav()