diff --git a/tests/backend/preview.test.js b/tests/backend/preview.test.js
new file mode 100644
index 0000000..202a856
--- /dev/null
+++ b/tests/backend/preview.test.js
@@ -0,0 +1,35 @@
+// 文件预览 API 测试
+const request = require('supertest');
+const app = require('../../backend/src/index');
+
+describe('Preview API', () => {
+  let token;
+  
+  beforeAll(async () => {
+    // Login first
+    const loginRes = await request(app)
+      .post('/api/auth/login')
+      .send({ username: 'testuser', password: 'test123' });
+    token = loginRes.body.token;
+  });
+
+  describe('GET /api/preview/:id', () => {
+    it('should get preview info', async () => {
+      const response = await request(app)
+        .get('/api/preview/1')
+        .set('Authorization', `Bearer ${token}`);
+      
+      expect(response.status).toBe(200);
+      expect(response.body).toHaveProperty('fileId');
+      expect(response.body).toHaveProperty('isPreviewable');
+    });
+
+    it('should reject invalid token', async () => {
+      const response = await request(app)
+        .get('/api/preview/1')
+        .set('Authorization', 'Bearer invalid');
+      
+      expect(response.status).toBe(401);
+    });
+  });
+});