Max range display is the guaranteed (worst-case headwind) full-tank range (ISS-099, v0.51.0)

lib/game/catalog.test.ts

@@ -1,6 +1,7 @@
 import { describe, expect, it } from 'vitest';
 import { FUEL_DISCOUNT_PER_REP, MAX_FUEL_DISCOUNT, MAX_PLANE_DISCOUNT, PLANE_DISCOUNT_PER_REP, PLANE_TYPES, repRate, STARTER_MODEL } from './catalog';
 import { STARTING_REPUTATION } from './seed';
+import { guaranteedRangeKm, MAX_WIND_BURN_FACTOR, maxRangeKm, requiredFuelFor } from '@/lib/sim/movement';
 
 // v0.28.0 (ISS-047) — catalog sanity: the progression ladder must stay well-formed as types are added.
 describe('PLANE_TYPES', () => {
@@ -43,3 +44,25 @@ describe('repRate', () => {
     expect(repRate(1_000_000, FUEL_DISCOUNT_PER_REP, MAX_FUEL_DISCOUNT)).toBe(MAX_FUEL_DISCOUNT);
   });
 });
+
+// v0.51.0 (ISS-099) — max range consistency: for EVERY catalog type the displayed guaranteed range
+// must be flyable on a full tank under worst-case headwind burn (the same requiredFuelFor ≤ maxFuel
+// rule as flyPlane's fuel guard), and tight — not padded. The closed form inverts exactly, so the
+// "≤" side allows only float noise (~1e-11 L → relative 1e-9 tolerance).
+describe('max range consistency (v0.51.0, ISS-099)', () => {
+  for (const t of Object.values(PLANE_TYPES)) {
+    it(`${t.id}: guaranteed range is flyable in worst-case headwind and not padded`, () => {
+      const r = guaranteedRangeKm(t.burnPerKm, t.emptyWeightKg, t.maxFuel);
+      expect(requiredFuelFor(t.burnPerKm * MAX_WIND_BURN_FACTOR, t.emptyWeightKg, t.maxFuel, r))
+        .toBeLessThanOrEqual(t.maxFuel * (1 + 1e-9));
+      // Tight: 5% beyond the displayed range no longer fits a full tank.
+      expect(requiredFuelFor(t.burnPerKm * MAX_WIND_BURN_FACTOR, t.emptyWeightKg, t.maxFuel, 1.05 * r))
+        .toBeGreaterThan(t.maxFuel);
+    });
+
+    it(`${t.id}: the no-wind closed form inverts requiredFuelFor exactly`, () => {
+      const r = maxRangeKm(t.burnPerKm, t.emptyWeightKg, t.maxFuel);
+      expect(requiredFuelFor(t.burnPerKm, t.emptyWeightKg, t.maxFuel, r)).toBeLessThanOrEqual(t.maxFuel * (1 + 1e-9));
+    });
+  }
+});