fix: enhance unit tests for AutoAgents class

- Added dynamic import handling for AutoAgents and related classes to prevent ImportError.
- Refactored test cases to create AutoAgents instances without invoking __init__ to avoid unnecessary API calls.
- Improved mock handling in tests to ensure proper validation and response checks.
- Ensured structured output support is correctly mocked across various test scenarios.
- Maintained existing functionality while optimising test structure for clarity and maintainability.

Author: MervinPraison