diff --git a/tests/CouponServiceTest.php b/tests/CouponServiceTest.php
new file mode 100644
index 0000000..9e58e6a
--- /dev/null
+++ b/tests/CouponServiceTest.php
@@ -0,0 +1,93 @@
+<?php
+
+namespace Bazaar\Tests;
+
+use Bazaar\Repositories\CouponRepository;
+use Bazaar\Services\CouponResult;
+use Bazaar\Services\CouponService;
+
+final class CouponServiceTest extends DatabaseTestCase
+{
+    private CouponRepository $coupons;
+    private CouponService $service;
+
+    protected function setUp(): void
+    {
+        parent::setUp();
+        $this->coupons = new CouponRepository($this->db);
+        $this->service = new CouponService($this->coupons);
+    }
+
+    private function coupon(array $overrides = []): int
+    {
+        return $this->coupons->create(array_merge([
+            'code' => 'SAVE10',
+            'type' => 'percent',
+            'value' => 10,
+            'minSubtotalCents' => 0,
+            'maxRedemptions' => null,
+            'startsAt' => null,
+            'expiresAt' => null,
+            'isActive' => true,
+        ], $overrides));
+    }
+
+    public function testPercentDiscountIsFloored(): void
+    {
+        $this->coupon(['code' => 'SAVE15', 'value' => 15]);
+        $result = $this->service->evaluate('SAVE15', 999);
+
+        $this->assertTrue($result->isValid());
+        $this->assertSame((int) floor(999 * 0.15), $result->discountCents);
+    }
+
+    public function testFixedDiscountNeverExceedsSubtotal(): void
+    {
+        $this->coupon(['code' => 'FLAT50', 'type' => 'fixed', 'value' => 5000]);
+        $result = $this->service->evaluate('FLAT50', 3000);
+
+        $this->assertTrue($result->isValid());
+        $this->assertSame(3000, $result->discountCents);
+    }
+
+    public function testCodeLookupIsCaseInsensitive(): void
+    {
+        $this->coupon();
+        $this->assertTrue($this->service->evaluate('save10', 5000)->isValid());
+    }
+
+    public function testUnknownCodeIsRejected(): void
+    {
+        $this->assertSame(CouponResult::notFound, $this->service->evaluate('NOPE', 5000)->status);
+    }
+
+    public function testInactiveCouponIsRejected(): void
+    {
+        $this->coupon(['code' => 'OFF', 'isActive' => false]);
+        $this->assertSame(CouponResult::inactive, $this->service->evaluate('OFF', 5000)->status);
+    }
+
+    public function testBelowMinimumIsRejected(): void
+    {
+        $this->coupon(['code' => 'BIG', 'minSubtotalCents' => 10000]);
+        $this->assertSame(CouponResult::belowMinimum, $this->service->evaluate('BIG', 5000)->status);
+    }
+
+    public function testExpiredAndNotStartedWindows(): void
+    {
+        $this->coupon(['code' => 'PAST', 'expiresAt' => '2020-01-01T00:00:00+00:00']);
+        $this->coupon(['code' => 'FUTURE', 'startsAt' => '2999-01-01T00:00:00+00:00']);
+
+        $this->assertSame(CouponResult::expired, $this->service->evaluate('PAST', 5000)->status);
+        $this->assertSame(CouponResult::notStarted, $this->service->evaluate('FUTURE', 5000)->status);
+    }
+
+    public function testExhaustedWhenRedemptionLimitReached(): void
+    {
+        $id = $this->coupon(['code' => 'ONCE', 'maxRedemptions' => 1]);
+        $this->assertTrue($this->service->evaluate('ONCE', 5000)->isValid());
+
+        $this->service->redeem($id);
+        $this->assertSame(CouponResult::exhausted, $this->service->evaluate('ONCE', 5000)->status);
+    }
+}