test contracts

backend/src/services/llm_provider.py

@@ -18,6 +18,18 @@ import os
 # @TIER: CRITICAL
 # @PURPOSE: Handles encryption and decryption of sensitive data like API keys.
 # @INVARIANT: Uses a secret key from environment or a default one (fallback only for dev).
+#
+# @TEST_CONTRACT: EncryptionManagerModel ->
+# {
+#   required_fields: {},
+#   invariants: [
+#       "encrypted data can be decrypted back to the original string"
+#   ]
+# }
+# @TEST_FIXTURE: basic_encryption_cycle -> {"data": "my_secret_key"}
+# @TEST_EDGE: decrypt_invalid_data -> raises Exception
+# @TEST_EDGE: empty_string_encryption -> {"data": ""}
+# @TEST_INVARIANT: symmetric_encryption -> verifies: [basic_encryption_cycle, empty_string_encryption]
 class EncryptionManager:
     # [DEF:EncryptionManager.__init__:Function]
     # @PURPOSE: Initialize the encryption manager with a Fernet key.