When implementing Apex managed sharing, it is crucial to test the sharing logic to ensure users are granted appropriate access to records. The runAs method allows developers to simulate record access for different users during testing, ensuring the implemented sharing logic functions correctly.

Option A: Using "Without Sharing" disables sharing enforcement, which is not appropriate for Apex-managed sharing scenarios.

Option B: The "With Sharing" keyword enforces sharing rules in the code but is not relevant for testing user access.

Option C (Correct): The runAs method is a best practice for simulating user-specific access during tests, ensuring the logic aligns with the organization’s sharing rules.