LocalData/Documentation/Testing.md

LocalData Testing Strategy

Goal

To ensure high reliability for data persistence, security, and migration across all supported platforms (iOS and watchOS).

Test Suites

Unit Tests (Tests/LocalDataTests/)

• LocalDataTests.swift: Core round-trip tests for each storage domain (UserDefaults, FileSystem).
• KeychainHelperTests.swift: Verification of Keychain API interactions (add, update, delete, exists).
• EncryptionHelperTests.swift: Round-trip tests for AES and ChaCha20 encryption/decryption with various key derivation methods.
• StorageCatalogTests.swift: Validation of catalog registration, duplicate detection, and missing description checks.

Key Testing Patterns

1. Domain Round-Trips

Always test the full cycle: set -> get (compare) -> remove -> get (expect notFound).

2. Migration Tests

Simulate legacy data by writing to a "legacy" key first, then verifying that the "modern" key can retrieve and consolidate that data.

3. Error Handling

Verify that the correct StorageError is thrown for:

• notFound
• unregisteredKey
• dataTooLargeForSync
• Domain-specific failures (e.g., Keychain errors)

Running Tests

Run all tests from the package root:

swift test