diff --git a/apps/pr-reviewer/fixtures/demo-pr/checkout-flow.integration.test.ts b/apps/pr-reviewer/fixtures/demo-pr/checkout-flow.integration.test.ts
index 7a5dc1f..99c56a2 100644
--- a/apps/pr-reviewer/fixtures/demo-pr/checkout-flow.integration.test.ts
+++ b/apps/pr-reviewer/fixtures/demo-pr/checkout-flow.integration.test.ts
@@ -4,6 +4,7 @@ import { describe, expect, it } from 'vitest';
 import { cartTotal } from './cart-total.ts';
 import { pointsFor } from './loyalty.ts';
 import { canRefund } from './refund-window.ts';
+import { shippingCost } from './shipping.ts';
 
 const DAY_MS = 86_400_000;
 const settle = () => new Promise((r) => setTimeout(r, 80_000));
@@ -50,4 +51,10 @@ describe('checkout flow', () => {
     expect(pointsFor(total)).toBe(3);
     await settle();
   });
+
+  it('charges the heavy rate for a 5 kg parcel', async () => {
+    expect(shippingCost(5)).toBe(12);
+    expect(shippingCost(5, true)).toBe(24);
+    await settle();
+  });
 });
diff --git a/apps/pr-reviewer/fixtures/demo-pr/shipping.ts b/apps/pr-reviewer/fixtures/demo-pr/shipping.ts
index ef54a04..191a75c 100644
--- a/apps/pr-reviewer/fixtures/demo-pr/shipping.ts
+++ b/apps/pr-reviewer/fixtures/demo-pr/shipping.ts
@@ -1,4 +1,4 @@
 export function shippingCost(weightKg: number, express = false): number {
-  const base = weightKg > 5 ? 12 : 6;
+  const base = weightKg >= 5 ? 12 : 6;
   return express ? base * 2 : base;
 }