diff --git a/tests/pricing.test.ts b/tests/pricing.test.ts
index 499c560..16c2b15 100644
--- a/tests/pricing.test.ts
+++ b/tests/pricing.test.ts
@@ -29,3 +29,39 @@ Deno.test('Batch cost calculation', () => {
   // 1 standard call
   assertEquals(calculateBatchCost(51, 1), 0.01);
 });
+
+
+Deno.test('Edge: zero calls returns free tier', () => {
+  assertEquals(getTierPrice(0).tier, 'free');
+  assertEquals(getTierPrice(0).pricePerCall, 0.00);
+});
+
+Deno.test('Edge: large call count still returns premium', () => {
+  assertEquals(getTierPrice(1000000).tier, 'premium');
+  assertEquals(getTierPrice(1000000).pricePerCall, 0.03);
+});
+
+Deno.test('Edge: negative call count defaults to free', () => {
+  assertEquals(getTierPrice(-1).tier, 'free');
+});
+
+Deno.test('Edge: priority flag at tier boundary', () => {
+  // Priority at different call counts should always return priority pricing
+  assertEquals(getTierPrice(1, true).pricePerCall, 0.10);
+  assertEquals(getTierPrice(50, true).pricePerCall, 0.10);
+  assertEquals(getTierPrice(51, true).pricePerCall, 0.10);
+  assertEquals(getTierPrice(500, true).pricePerCall, 0.10);
+  assertEquals(getTierPrice(501, true).pricePerCall, 0.10);
+});
+
+Deno.test('Edge: batch cost with mixed tiers', () => {
+  // 50 free calls + 1 standard = /usr/bin/bash.01
+  const cost = calculateBatchCost(1, 51);
+  assertEquals(cost > 0, true);
+});
+
+Deno.test('Migration is idempotent', async () => {
+  const sql = await Deno.readTextFile('./migrations/add_tiered_pricing.sql');
+  assertEquals(sql.includes('IF NOT EXISTS'), true);
+  assertEquals(sql.includes('ON CONFLICT'), true);
+});