Write Unit Tests for Python Function

I need help writing comprehensive unit tests for a Python function using pytest. Please generate well-structured tests that thoroughly verify the function's behavior. Here is the function to test: ```python [PASTE FUNCTION CODE HERE] ``` Please create a complete set of pytest unit tests that: 1. TEST COVERAGE * Tests all main functionality of the function * Covers expected use cases and edge cases * Includes both valid and invalid inputs * Tests error conditions and exceptions * Achieves high code coverage 2. TEST ORGANIZATION * Uses clear test function names that describe what's being tested * Groups related tests logically * Follows pytest best practices and conventions * Uses appropriate fixtures when needed * Includes setup and teardown code if necessary 3. ASSERTIONS & VALIDATION * Uses appropriate pytest assertions * Includes clear failure messages * Validates all relevant aspects of the function's output * Checks both return values and side effects if applicable * Verifies exceptions with proper context 4. MOCKING & ISOLATION * Isolates the function from external dependencies when appropriate * Uses mocks, patches, or stubs as needed * Demonstrates how to test the function independently * Shows how to simulate different scenarios 5. TEST DOCUMENTATION * Includes docstrings explaining test purpose * Comments explaining complex test logic * Demonstrates usage patterns through tests * Provides context for why specific test cases are important Please provide the complete test file that I can directly use with pytest, including all necessary imports and any helper functions or fixtures needed to make the tests run successfully.