Testing¶

This skill covers testing patterns and edge cases specific to HoloViz repositories.

General Guidelines¶

Run tests via pixi. Check pixi.toml for tasks (e.g. pixi run test-unit, pixi run test-ui).
New tests must fail on main before submitting.
UI tests require the --ui flag.
Only create a new test file if no existing file is a good fit.

Edge Cases and Logical Errors¶

Identify logical errors and edge cases in the changed code. Trace branching logic and boundary conditions to find inputs that could produce wrong results, silent data loss, or unexpected exceptions.
Test for NaN and datetime types (np, pd) — these are common edge cases across HoloViz that are easy to miss.
Parameterize tests when the same logic is exercised with different inputs.

# WRONG — only tests the happy path
def test_filter_by_range():
    df = pd.DataFrame({'x': [1, 2, 3]})
    result = filter_by_range(df, 'x', low=1, high=3)
    assert len(result) == 3

# CORRECT — covers edge cases and logical boundaries
@pytest.mark.parametrize(
    ("data", "low", "high", "expected_len"),
    [
        ([1, 2, 3], 1, 3, 3),
        ([1, 2, 3], 2, 2, 1),
        ([1, 2, 3], 5, 10, 0),
        ([], 0, 1, 0),
        ([np.nan, 1, 2], 0, 2, 2),
        ([1, 2, None], 0, 2, 2),
    ],
    ids=[
        "inclusive_bounds",
        "single_value_range",
        "no_matches",
        "empty_input",
        "nan_values",
        "none_values",
    ],
)

def test_filter_by_range(data, low, high, expected_len):
    df = pd.DataFrame({'x': data})
    result = filter_by_range(df, 'x', low=low, high=high)
    assert len(result) == expected_len