Abandon test suite for loops for pytest best practices

[kurtmckee]

for loops in the test suite have significant disadvantages. Among them: a single failing test input causes the entire test to fail, rather than failing the specific input combinations that can cause failure.

While pytest output can help identify the specific failure inputs in the for loop, the best practice is to use pytest.mark.parametrize; this allows pytest to handle each parameter independently.

This PR swaps out for loops in the test suite with pytest's pytest.mark.parametrize decorator.

[kurtmckee]

Rebased on main to (ideally) resolve the CI failures caused by the past ruff error.