diff --git a/tests/Feature/AdminSubscriptionActivationRenewalExtendsEndsAtTest.php b/tests/Feature/AdminSubscriptionActivationRenewalExtendsEndsAtTest.php
new file mode 100644
index 0000000..d9b78fe
--- /dev/null
+++ b/tests/Feature/AdminSubscriptionActivationRenewalExtendsEndsAtTest.php
@@ -0,0 +1,151 @@
+<?php
+
+namespace Tests\Feature;
+
+use App\Models\Merchant;
+use App\Models\Plan;
+use App\Models\PlatformOrder;
+use App\Models\SiteSubscription;
+use App\Support\SubscriptionActivationService;
+use Illuminate\Foundation\Testing\RefreshDatabase;
+use Tests\TestCase;
+
+class AdminSubscriptionActivationRenewalExtendsEndsAtTest extends TestCase
+{
+    use RefreshDatabase;
+
+    public function test_activate_order_will_extend_existing_subscription_ends_at(): void
+    {
+        $this->seed();
+
+        $merchant = Merchant::query()->firstOrFail();
+
+        $plan = Plan::query()->create([
+            'code' => 'renew_extend_test',
+            'name' => '续期延长到期测试（月付）',
+            'billing_cycle' => 'monthly',
+            'price' => 99,
+            'list_price' => 99,
+            'status' => 'active',
+            'sort' => 10,
+            'published_at' => now(),
+        ]);
+
+        // 构造一个仍有效的订阅：ends_at 在未来
+        $sub = SiteSubscription::query()->create([
+            'merchant_id' => $merchant->id,
+            'plan_id' => $plan->id,
+            'status' => 'activated',
+            'source' => 'manual',
+            'subscription_no' => 'SUB_RENEW_EXT_0001',
+            'plan_name' => $plan->name,
+            'billing_cycle' => $plan->billing_cycle,
+            'period_months' => 1,
+            'amount' => 99,
+            'starts_at' => now()->subDays(10),
+            'ends_at' => now()->addDays(20),
+            'activated_at' => now()->subDays(10),
+        ]);
+
+        $oldEndsAt = $sub->ends_at->copy();
+
+        // 构造一笔续费订单，绑定该订阅，购买 2 个月（period_months=1, quantity=2 => months=2）
+        $order = PlatformOrder::query()->create([
+            'merchant_id' => $merchant->id,
+            'plan_id' => $plan->id,
+            'site_subscription_id' => $sub->id,
+            'order_no' => 'PO_RENEW_EXT_0001',
+            'order_type' => 'renewal',
+            'status' => 'activated',
+            'payment_status' => 'paid',
+            'plan_name' => $plan->name,
+            'billing_cycle' => $plan->billing_cycle,
+            'period_months' => 1,
+            'quantity' => 2,
+            'list_amount' => 198,
+            'discount_amount' => 0,
+            'payable_amount' => 198,
+            'paid_amount' => 198,
+            'placed_at' => now()->subMinutes(10),
+            'paid_at' => now()->subMinutes(5),
+            'activated_at' => now()->subMinutes(1),
+        ]);
+
+        $service = app(SubscriptionActivationService::class);
+        $service->activateOrder($order->id, 1);
+
+        $sub->refresh();
+
+        $this->assertTrue($sub->ends_at->greaterThan($oldEndsAt));
+        $this->assertSame(
+            $oldEndsAt->copy()->addMonthsNoOverflow(2)->format('Y-m-d H:i:s'),
+            $sub->ends_at->format('Y-m-d H:i:s')
+        );
+    }
+
+    public function test_activate_order_will_extend_expired_subscription_from_now(): void
+    {
+        $this->seed();
+
+        $merchant = Merchant::query()->firstOrFail();
+
+        $plan = Plan::query()->create([
+            'code' => 'renew_extend_test2',
+            'name' => '续期延长到期测试（已过期）',
+            'billing_cycle' => 'monthly',
+            'price' => 99,
+            'list_price' => 99,
+            'status' => 'active',
+            'sort' => 10,
+            'published_at' => now(),
+        ]);
+
+        // 构造一个已过期订阅：ends_at 在过去
+        $sub = SiteSubscription::query()->create([
+            'merchant_id' => $merchant->id,
+            'plan_id' => $plan->id,
+            'status' => 'cancelled',
+            'source' => 'manual',
+            'subscription_no' => 'SUB_RENEW_EXT_0002',
+            'plan_name' => $plan->name,
+            'billing_cycle' => $plan->billing_cycle,
+            'period_months' => 1,
+            'amount' => 99,
+            'starts_at' => now()->subMonths(2),
+            'ends_at' => now()->subDays(1),
+            'activated_at' => now()->subMonths(2),
+            'cancelled_at' => now()->subDays(1),
+        ]);
+
+        // 续费 1 个月
+        $order = PlatformOrder::query()->create([
+            'merchant_id' => $merchant->id,
+            'plan_id' => $plan->id,
+            'site_subscription_id' => $sub->id,
+            'order_no' => 'PO_RENEW_EXT_0002',
+            'order_type' => 'renewal',
+            'status' => 'activated',
+            'payment_status' => 'paid',
+            'plan_name' => $plan->name,
+            'billing_cycle' => $plan->billing_cycle,
+            'period_months' => 1,
+            'quantity' => 1,
+            'list_amount' => 99,
+            'discount_amount' => 0,
+            'payable_amount' => 99,
+            'paid_amount' => 99,
+            'placed_at' => now()->subMinutes(10),
+            'paid_at' => now()->subMinutes(5),
+            'activated_at' => now()->subMinutes(1),
+        ]);
+
+        $service = app(SubscriptionActivationService::class);
+        $service->activateOrder($order->id, 1);
+
+        $sub->refresh();
+
+        $this->assertSame('activated', $sub->status);
+        $this->assertNotNull($sub->ends_at);
+        $this->assertTrue($sub->ends_at->greaterThan(now()));
+    }
+}