chore: move ccw-skill-hub to standalone repository

Migrated ccw-skill-hub to D:/ccw-skill-hub as independent git project.
Removed nested git repos (ccw/frontend/ccw-skill-hub, skill-hub-repo, skill-hub-temp).

codex-lens/tests/test_migrations.py

@@ -0,0 +1,114 @@
+"""Database Migration Tests.
+
+This module tests the database migration system for the codex-lens index,
+ensuring that forward and backward compatibility is maintained across schema versions.
+
+Test Coverage:
+- Forward migrations: Old schema to new schema
+- Backward compatibility: New code can read old schemas
+- Migration rollback capabilities
+- Data integrity during migrations
+- Edge cases (empty databases, corrupted data, etc.)
+"""
+
+import pytest
+import sqlite3
+from pathlib import Path
+import tempfile
+import json
+
+
+class TestForwardMigrations:
+    """Test upgrading from older schema versions to newer ones."""
+
+    def test_v0_to_v1_migration(self):
+        """Test migration from schema v0 to v1."""
+        pytest.skip("Requires migration infrastructure setup")
+
+    def test_v1_to_v2_migration(self):
+        """Test migration from schema v1 to v2."""
+        pytest.skip("Requires migration infrastructure setup")
+
+    def test_migration_preserves_data(self):
+        """Test that migration preserves existing data."""
+        pytest.skip("Requires migration infrastructure setup")
+
+    def test_migration_adds_new_columns(self):
+        """Test that new columns are added with correct defaults."""
+        pytest.skip("Requires migration infrastructure setup")
+
+
+class TestBackwardCompatibility:
+    """Test that newer code can read and work with older database schemas."""
+
+    def test_new_code_reads_old_schema(self):
+        """Test that current code can read old schema databases."""
+        pytest.skip("Requires old schema fixture")
+
+    def test_new_code_writes_to_old_schema(self):
+        """Test that current code handles writes to old schema gracefully."""
+        pytest.skip("Requires old schema fixture")
+
+    def test_old_code_rejects_new_schema(self):
+        """Test that old code fails appropriately on new schemas."""
+        pytest.skip("Requires old code fixture")
+
+
+class TestMigrationRollback:
+    """Test rollback capabilities for failed migrations."""
+
+    def test_failed_migration_rolls_back(self):
+        """Test that failed migrations are rolled back completely."""
+        pytest.skip("Requires migration infrastructure setup")
+
+    def test_partial_migration_recovery(self):
+        """Test recovery from partially completed migrations."""
+        pytest.skip("Requires migration infrastructure setup")
+
+    def test_rollback_preserves_original_data(self):
+        """Test that rollback restores original state."""
+        pytest.skip("Requires migration infrastructure setup")
+
+
+class TestMigrationEdgeCases:
+    """Test migration behavior in edge cases."""
+
+    def test_empty_database_migration(self):
+        """Test migration of an empty database."""
+        pytest.skip("Requires migration infrastructure setup")
+
+    def test_large_database_migration(self):
+        """Test migration of a large database."""
+        pytest.skip("Requires migration infrastructure setup")
+
+    def test_corrupted_database_handling(self):
+        """Test handling of corrupted databases during migration."""
+        pytest.skip("Requires migration infrastructure setup")
+
+    def test_concurrent_migration_protection(self):
+        """Test that concurrent migrations are prevented."""
+        pytest.skip("Requires migration infrastructure setup")
+
+
+class TestSchemaVersionTracking:
+    """Test schema version tracking and detection."""
+
+    def test_version_table_exists(self):
+        """Test that version tracking table exists and is populated."""
+        pytest.skip("Requires migration infrastructure setup")
+
+    def test_version_auto_detection(self):
+        """Test that schema version is auto-detected from database."""
+        pytest.skip("Requires migration infrastructure setup")
+
+    def test_version_update_after_migration(self):
+        """Test that version is updated correctly after migration."""
+        pytest.skip("Requires migration infrastructure setup")
+
+
+# TODO: Implement actual tests using pytest fixtures
+# The test infrastructure needs:
+# - Migration runner fixture that can apply and rollback migrations
+# - Old schema fixtures (pre-built databases with known schemas)
+# - Temporary database fixtures for isolated testing
+# - Mock data generators for various schema versions