Testing

The suite is laid out like mplhep's. Where mplhep uses pytest-mpl, tests/conftest.py provides the same idea for Plotly:

@pytest.mark.image_compare(tolerance=4, remove_text=True)
def test_histplot_step():
    fig = php.figure()
    php.histplot(fig, [h1, h2], bins, label=["a", "b"])
    return fig      # rendered with kaleido, RMS-compared with tests/baseline/test_histplot_step.png

remove_text=True strips annotations, titles, tick labels, colorbar labels and the legend before rendering, so a baseline tests geometry rather than fonts. pytest --regen-baselines rewrites the baselines after an intentional visual change; a failure saves actual, expected and diff images under tests/output/failed/.

Tests that keep their text rely on the conftest pinning fontconfig to the font files that mplhep-data ships, and nothing else. matplotlib lays text out from those files itself, so it renders the same everywhere; kaleido's Chromium takes whatever fontconfig offers, and two builds of the same TeX Gyre Heros moved a top-anchored label by ten pixels between a laptop and the CI runner. With both stacks reading the same bytes the baselines are portable. PLOTLYHEP_SYSTEM_FONTS=1 turns the pin off.

file	covers
test_basic.py	histplot step / fill / errorbar / stack / density, hist2dplot
test_styles.py	template values from mplhep's rcParams, use, root_template, transparent JSON
test_labels.py	exp_text / exp_label geometry for loc 0–4, the lumi line, axis-label helpers
test_layouts.py	ratio-panel domains against matplotlib's own GridSpec, ratioplot values
test_convert.py, test_html.py, test_inputs.py	conversion, embeds, input shapes
test_hover.py	hover content, probed headlessly
test_pixel.py + compare.py	the same figure through mplhep and plotlyhep at 1000×1000, ratchet thresholds
test_root.py + compare_root.py	the gallery rebuilds against ROOT's tutorial images

pip install -e ".[dev]"
pytest                    # 79 tests, about 6 s
nox                       # lint (ruff, ruff format, mypy, codespell) and the test matrix
mkdocs serve              # this site, live