CellularAndSminGradTests pins the rules the cut map calls out, each against a
mutant it must kill:
- smin's value never exceeds the ordinary minimum, and matches min with that
input's own gradient once |a.w - b.w| exceeds k on either side.
- smin_grad's gradient matches central differences of its own .w at random
seeded points (the formula is exact, not an approximation, so no exclusion
band is needed away from the |a.w-b.w|=k seam itself).
- A direct case falsifies blending the gradient with a constant 0.5 or with
(1 - h) instead of h.
- cellular's F1 never exceeds F2, matched against an independent brute-force
Worley search that shares only the public pcg3d hash, not cellular's control
flow.
- The true nearest feature wins even when an independent search finds it in
the (1, 1, 1) neighbour offset, the last one cellular's own loop order
visits, ruling out a "first found" or early-exit mutant.
- The gradient at a feature point is finite zero, not NaN.
- Both nearest and edge gradients match central differences away from a band
around the F1 = F2 set, where the nearest and second-nearest identity swap
discontinuously.
- id is constant across small moves that stay in the same feature's region and
differs from a distant cell's id.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
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