Synthetic fixtures (deterministic)

Principles

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  Deterministic by default (no RNG), or seeded RNG only.

• •

  Tests should check:

  • •geometry error (px)
  • •stability under small noise/blur
  • •edge cases (odd sizes, borders, ROI truncation)

Useful fixtures

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  Half-plane step edge with known line equation (slanted edge):

  • •I(p)=A if dot(n, p) < t else B
  • •Optional blur along n (binomial/gaussian-ish) to make it realistic
• •

  Stripe (laser) as difference of two steps (bright-on-dark):

  • •known left/right subpixel positions → known center + width
• •

  Circle / ring boundary (later):

  • •implicit distance function d = sqrt((x-cx)^2+(y-cy)^2)-r
  • •intensity from sign(d) and controlled blur

Expected-value checks

• •Keep early tests loose (~0.1–0.2 px).
• •Add tighter tests later (aim 0.05 px) on higher-fidelity fixtures.

Regression strategy

• •When a bug appears, capture it as a small synthetic fixture.