Write unit test cases for all functions #113
Description
Add comprehensive unit tests for all functions to ensure reliability and maintainability.
The tests should mock the node-appwrite SDK to avoid real API calls and verify that each function:
- Calls the correct Appwrite methods with expected parameters.
- Returns the correct values on success.
- Handles and propagates errors properly.
Use Jest for testing, and include both positive and negative scenarios for full coverage.