test: add API route tests

src/app/api/auth/[...nextauth]/route.test.ts

@@ -0,0 +1,39 @@
+import { GET, POST } from './route';
+
+jest.mock('@/lib/auth', () => ({
+  handlers: {
+    GET: jest.fn(() => new Response('GET response')),
+    POST: jest.fn(() => new Response('POST response')),
+  },
+}));
+
+describe('/api/auth/[...nextauth]', () => {
+  describe('GET handler', () => {
+    it('should export GET handler', () => {
+      expect(typeof GET).toBe('function');
+    });
+
+    it('should call auth GET handler', async () => {
+      const response = await GET(new Request('http://localhost/api/auth/signin'));
+      expect(response).toBeDefined();
+      expect(response.status).toBe(200);
+    });
+  });
+
+  describe('POST handler', () => {
+    it('should export POST handler', () => {
+      expect(typeof POST).toBe('function');
+    });
+
+    it('should call auth POST handler', async () => {
+      const response = await POST(
+        new Request('http://localhost/api/auth/signin', {
+          method: 'POST',
+          body: JSON.stringify({ email: 'test@example.com', password: 'password' }),
+        })
+      );
+      expect(response).toBeDefined();
+      expect(response.status).toBe(200);
+    });
+  });
+});