polygonize: close test-coverage gaps for backends, edge cases, params#2156
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Deep-sweep test-coverage pass 1 (2026-05-19): adds
test_polygonize_coverage_2026_05_19.py with 58 tests, all passing on
a CUDA host.
Closes the following audit-flagged gaps:
Cat 1 (backend coverage)
- simplify_tolerance + mask= parity on the dask+cupy backend
(numpy / cupy / dask were already covered).
Cat 2 (NaN / Inf / nodata)
- NaN parity for cupy and dask+cupy.
- all-NaN raster on every backend.
- +/-Inf pins on every backend. numpy / dask / dask+cupy currently
silently absorb Inf cells into adjacent finite polygons (issue
#2155); cupy emits them correctly. Pins lock the asymmetric
behaviour so the fix is visible.
Cat 3 (geometric)
- 1x1 single-pixel raster on all four backends + geopandas.
- Nx1 single-column raster exercises the nx==1 padding path
(polygonize.py:565) and the cupy nx==1 numpy-fallback
(polygonize.py:671).
- 1xN single-row and all-equal-value rasters on all four backends.
Cat 4 (parameter coverage)
- column_name non-default value across geopandas / spatialpandas /
geojson return types.
- Validation error paths: bad connectivity, bad transform length,
mask shape mismatch, mask underlying-type mismatch.
Cat 5 N/A: polygonize returns lists / dataframes, not a DataArray
with attrs to propagate.
Self-review of #2156 surfaced four loose assertions that would let regressions slip past: - test_dask_cupy_inf_emits_polygons used an if/else with identical inner assertions, so it never failed regardless of behaviour. The dask+cupy backend actually undercounts today (consistent with the numpy/dask bug, since _polygonize_chunk routes through the numpy backend per chunk). Rename to *_currently_undercounts and pin that explicitly so the #2155 source fix is visible as a diff. - test_dask_inf_currently_undercounts only asserted the absence of Inf polygons. Mirror the numpy sibling's area + value=1.0 conservation checks so a regression that loses a finite polygon is also caught. - TestSimplifyDaskCupy.test_dask_cupy_matches_numpy_areas iterated over a_np keys without asserting set equality, so an extra dask+cupy polygon class would have been silently ignored. - test_column_name_geopandas_non_default asserted DataFrame row order, which is implementation-defined. Sort before comparing.
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Summary
Deep-sweep test-coverage pass against
xrspatial/polygonize.pyon 2026-05-19. Addsxrspatial/tests/test_polygonize_coverage_2026_05_19.pywith 58 tests, all passing on a CUDA host.Gaps closed
Cat 1 (backend coverage)
simplify_tolerance=andmask=parity on the dask+cupy backend. numpy / cupy / dask were already covered.Cat 2 (NaN / Inf / nodata)
Cat 3 (geometric edge cases)
nx==1padding path atpolygonize.py:565and the cupynx==1numpy-fallback atpolygonize.py:671. Neither code path had direct test coverage before.Cat 4 (parameter coverage)
column_name=non-default value across geopandas / spatialpandas / geojson return types.connectivity, badtransformlength, mask shape mismatch, mask underlying-type mismatch.Cat 5 not applicable: polygonize returns lists / dataframes, not a
DataArraywith attrs to propagate.Source-bug surfaced
Filed #2155 for a real bug surfaced by the +/-Inf tests: numpy / dask / dask+cupy backends silently absorb Inf cells. Per sweep rules the source fix is NOT bundled with this test-only PR.
Test plan
python -m pytest xrspatial/tests/test_polygonize_coverage_2026_05_19.py-> 58 passed.python -m pytest xrspatial/tests/test_polygonize.py xrspatial/tests/test_polygonize_coverage_2026_05_19.py-> 172 passed, 13 skipped (pre-existing skips for optional deps).