import pytest
from module import function_to_test

class TestFunctionName:
    """Tests for function_name."""

    def test_basic_case(self):
        """Test the basic/happy path."""
        result = function_to_test(valid_input)
        assert result == expected_output

    def test_edge_case(self):
        """Test edge cases."""
        ...

    def test_error_handling(self):
        """Test error conditions."""
        with pytest.raises(ExpectedError):
            function_to_test(invalid_input)

@pytest.mark.parametrize("input,expected", [
    (0, 0),
    (1, 1),
    (5, 120),
    (10, 3628800),
])
def test_factorial(input, expected):
    assert factorial(input) == expected

import pytest

@pytest.mark.asyncio
async def test_async_function():
    result = await async_function()
    assert result == expected