Test floating-point distance boundaries without inverse round trips

For a strict floating-point distance gate, test the inclusive comparator separately from the coordinate-to-distance calculation. Constructing a point with an inverse geodesic formula does not guarantee that the forward formula returns the exact threshold: rounding can put the fixture slightly outside it. Use an exact computed-distance test double for equality, alongside real-coordinate cases just inside and outside the boundary. Do not widen the production threshold merely to make the inverse-generated fixture pass. This proves comparator and nearby distance behavior separately; it does not establish real GPS accuracy.

Applies when: testing geographic distance thresholds implemented with floating-point arithmetic. Keywords: geofence distance boundary floating point rounding Haversine tests