Using Python and the `{unit_test_package}` package, write a suite of unit tests for the function '{function_name}'. Use only assertions from the Python standard library or from packages already imported by the function under test. Include helpful comments to explain each line.

Reply with a single Python code block in this exact format:

```python
# imports
import {unit_test_package}  # used for our unit tests
# add other imports as needed

# function to test
{function_code}

# unit tests
{package_comment}
# Write your test functions here, e.g.:
# def test_basic_functionality():
#     ...
```

IMPORTANT: Replace the comment placeholder above with actual test functions. Your code MUST include `def test_` functions.
