feat(cache): add FileCache tests and fix Date serialization

[gmickel]

FileCache Tests and Date Serialization Fix

Problem

1. The FileCache class lacked comprehensive unit tests, making it difficult to verify its behavior and catch potential regressions.
2. Date objects were not being properly handled during serialization and deserialization in the FileCache, causing inconsistencies between original and cached FileInfo objects.

Solution

This PR addresses both issues:

1. Comprehensive Unit Tests:

   • Implemented a new test file tests/unit/file-cache.test.ts
   • Added tests covering key FileCache functionalities including:
     • Storing and retrieving file information
     • Handling non-existent files
     • Updating cache when file content changes
     • Persisting cache to disk and loading it
     • Clearing the cache

2. Date Serialization Fix:

   • Implemented custom JSON parsing and stringifying methods in FileCache to ensure proper handling of Date objects:
     • In loadCache: Added a custom reviver function to JSON.parse to convert ISO date strings back into Date objects
     • In saveCache: Added a custom replacer function to JSON.stringify to convert Date objects to ISO string format

Changes

• Added new file tests/unit/file-cache.test.ts
• Modified src/utils/file-cache.ts:
  • Updated loadCache method with custom JSON parsing
  • Updated saveCache method with custom JSON stringifying

Testing

The new test suite in file-cache.test.ts covers the core functionality of FileCache, including the proper handling of Date objects. These tests ensure that:

• File information is correctly stored and retrieved
• The cache is properly persisted to disk and can be reloaded
• Date objects are correctly serialized and deserialized