Test 2: Checking deep merge of nested objects...
ERROR: Deep merge failed:
  - server.timeout should be 30 (preserved), got None
  - server.ssl.enabled should be true (overridden)
  - server.ssl.cert should exist (added from override)
  - database.type should be 'postgres' (preserved)
  - database.pool.max should be 20 (overridden)
  - database.pool.min should be 2 (preserved)
  - database.pool.idle should exist (added)