stop the server after test

calendar.test.js

@@ -25,6 +25,8 @@ describe('Calendar Merging API', () => {
         if (fs.existsSync(MERGED_CALENDARS_DIR)) {
             fs.rmdirSync(MERGED_CALENDARS_DIR, { recursive: true });
         }
+        // Close the server
+        await new Promise(resolve => server.close(resolve));
     });
 
     test('Merge date-based calendar', async () => {