Test: guard site subscriptions index back param no nesting

tests/Feature/AdminSiteSubscriptionIndexBackParamDoesNotNestTest.php

@@ -0,0 +1,90 @@
+<?php
+
+namespace Tests\Feature;
+
+use App\Models\Merchant;
+use App\Models\Plan;
+use App\Models\PlatformOrder;
+use App\Models\SiteSubscription;
+use Illuminate\Foundation\Testing\RefreshDatabase;
+use Tests\TestCase;
+
+class AdminSiteSubscriptionIndexBackParamDoesNotNestTest extends TestCase
+{
+    use RefreshDatabase;
+
+    protected function loginAsPlatformAdmin(): void
+    {
+        $this->seed();
+
+        $this->post('/admin/login', [
+            'email' => 'platform.admin@demo.local',
+            'password' => 'Platform@123456',
+        ])->assertRedirect('/admin');
+    }
+
+    public function test_subscription_index_back_param_should_not_nest_back(): void
+    {
+        $this->loginAsPlatformAdmin();
+
+        $merchant = Merchant::query()->firstOrFail();
+        $plan = Plan::query()->create([
+            'code' => 'sub_index_back_no_nest_plan',
+            'name' => '订阅列表 back 防嵌套测试套餐',
+            'billing_cycle' => 'monthly',
+            'price' => 10,
+            'list_price' => 10,
+            'status' => 'active',
+            'sort' => 10,
+            'published_at' => now(),
+        ]);
+
+        $sub = SiteSubscription::query()->create([
+            'merchant_id' => $merchant->id,
+            'plan_id' => $plan->id,
+            'status' => 'activated',
+            'source' => 'manual',
+            'subscription_no' => 'SUB_INDEX_BACK_NO_NEST_0001',
+            'plan_name' => $plan->name,
+            'billing_cycle' => $plan->billing_cycle,
+            'period_months' => 1,
+            'amount' => 10,
+            'starts_at' => now()->subDay(),
+            'ends_at' => now()->addMonth(),
+            'activated_at' => now()->subDay(),
+        ]);
+
+        PlatformOrder::query()->create([
+            'merchant_id' => $merchant->id,
+            'plan_id' => $plan->id,
+            'site_subscription_id' => $sub->id,
+            'order_no' => 'PO_SUB_INDEX_BACK_NO_NEST_0001',
+            'order_type' => 'renewal',
+            'status' => 'activated',
+            'payment_status' => 'paid',
+            'plan_name' => $plan->name,
+            'billing_cycle' => $plan->billing_cycle,
+            'period_months' => 1,
+            'quantity' => 1,
+            'payable_amount' => 10,
+            'paid_amount' => 10,
+            'placed_at' => now(),
+            'paid_at' => now(),
+            'activated_at' => now(),
+        ]);
+
+        $incomingBack = '/admin/platform-orders?status=pending';
+
+        $res = $this->get('/admin/site-subscriptions?status=activated&back=' . urlencode($incomingBack));
+        $res->assertOk();
+
+        // 期望：订阅列表页生成的 back 只应指向“当前列表（去掉 back 参数）”，不应无限嵌套 back
+        $expectedBack = urlencode('/admin/site-subscriptions?status=activated');
+
+        $res->assertSee('/admin/site-subscriptions/' . $sub->id . '?back=' . $expectedBack, false);
+        $res->assertSee('/admin/platform-orders?site_subscription_id=' . $sub->id . '&back=' . $expectedBack, false);
+
+        // 若发生 back 嵌套，通常会出现 back=...back%3D... 这样的结构
+        $res->assertDontSee('back%3D', false);
+    }
+}