Node Application test via jest and supertest keep failing - node.js

Question

I have a MERN stack application that I am running a test on using jest and supertest. I am new to testing and was following a tutorial. However, mine keep failing. My MERN stack application has redis database instance for storing users' refresh token. It also uses node crone to carry out scheduled background tasks.
I am getting these errors when I ran my tests:
thrown: "Exceeded timeout of 5000 ms for a test.
Use jest.setTimeout(newTimeout) to increase the timeout value, if this is a long-running test."
And this error:
Jest did not exit one second after the test run has completed.
This usually means that there are asynchronous operations that weren't stopped in your tests.
Consider running Jest with `--detectOpenHandles` to troubleshoot this issue.
I have used npm test --detectOpenHandles to see if I could detect the asynchronous operations but I didnt see any. Like, it wasn't revealed.
Here is my test:
const request = require('supertest')
const app = require('../app')
describe('Test POST /register', ()=>{
test('It should respond with 200 success', async ()=>{
const response = await request(app).post('/register');
expect(response.statusCode).toBe(200);
},);
test('It should catch password must be present', ()=>{});
})
I have tried adding this line of code to the test:
afterAll(async () => { await app.close(); });
It didn't resolve it. I have also tried adding done(), it didn't work too. I have also increased the timeOut which I added as second argument in test, still the same thing.
I am testing my routes and here is the current one I tried which is register route.
router.post('/register', register);
Here is the app.js file
app.use("/api/v1/auth", authRoute);
app.use("/api/v1/users",userRoute);
app.get('*', (req, res)=>{
res.sendFile(path.join(__dirname, 'build', 'index.html'));
})
app.use(checkDB);
module.exports = app;
Here is the server.js
const http = require('http');
require('dotenv').config();;//declaring the envy file
const app = require('./app');
//mongoDb
const connectDB = require('./db/connect');
const port = process.env.PORT || 5000;
const server = http.createServer(app);
const start = async () => {
try {
await connectDB(process.env.MONGO_URL)
server.listen(port, () =>
console.log(`Server is listening on port ${port}...`)
);
} catch (error) {
console.log(error);
}
};
start();