diff --git a/tests/Feature/AdminMerchantIndexUsesExternalCssTest.php b/tests/Feature/AdminMerchantIndexUsesExternalCssTest.php
new file mode 100644
index 0000000..f937a84
--- /dev/null
+++ b/tests/Feature/AdminMerchantIndexUsesExternalCssTest.php
@@ -0,0 +1,37 @@
+<?php
+
+namespace Tests\Feature;
+
+use Illuminate\Foundation\Testing\RefreshDatabase;
+use Tests\TestCase;
+
+class AdminMerchantIndexUsesExternalCssTest 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_admin_merchants_index_should_not_include_inline_style_blocks(): void
+    {
+        $this->loginAsPlatformAdmin();
+
+        $res = $this->get('/admin/merchants');
+        $res->assertOk();
+
+        $html = (string) $res->getContent();
+
+        // 样式治理：后台页面不应新增大段 inline <style>
+        $this->assertStringNotContainsString('<style', $html);
+
+        // 并且应包含统一的后台样式文件
+        $this->assertStringContainsString('/css/admin-components.css', $html);
+    }
+}