平台订单详情：关联订阅链接补齐 back 且避免 back 嵌套

tests/Feature/AdminPlatformOrderShowRelatedSubscriptionLinksShouldNotNestBackTest.php

@@ -0,0 +1,82 @@
+<?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 AdminPlatformOrderShowRelatedSubscriptionLinksShouldNotNestBackTest 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_related_subscription_links_back_should_not_contain_nested_back(): void
+    {
+        $this->loginAsPlatformAdmin();
+
+        $merchant = Merchant::query()->firstOrFail();
+        $plan = Plan::query()->create([
+            'code' => 'po_show_related_sub_no_nested_back_plan',
+            'name' => '平台订单详情关联订阅 back 不嵌套测试套餐',
+            '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_PO_SHOW_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(),
+        ]);
+
+        $order = PlatformOrder::query()->create([
+            'merchant_id' => $merchant->id,
+            'plan_id' => $plan->id,
+            'site_subscription_id' => $sub->id,
+            'order_no' => 'PO_SHOW_NO_NEST_0001',
+            'order_type' => 'new_purchase',
+            'status' => 'pending',
+            'payment_status' => 'unpaid',
+            'plan_name' => $plan->name,
+            'billing_cycle' => $plan->billing_cycle,
+            'period_months' => 1,
+            'quantity' => 1,
+            'payable_amount' => 10,
+            'paid_amount' => 0,
+            'placed_at' => now(),
+            'meta' => [],
+        ]);
+
+        // 带 back 访问订单详情页（模拟从列表进入）
+        $res = $this->get('/admin/platform-orders/' . $order->id . '?back=' . urlencode('/admin/platform-orders?status=pending'));
+        $res->assertOk();
+
+        // 关联订阅的 back 应该回到“订单详情（去掉 back）”，不应出现 back=...back= 的嵌套
+        $res->assertDontSee('back%3D', false);
+    }
+}