Jest clear mocks between test cases (javascript)

I have this simple nodeJS application

const express = require('express')
const app = express()
const port = 3000

import {testFunction} from './util'

app.get('/', (req, res) => {
    console.log(testFunction(), 'result of testFunction')
    res.send('Hello World!')
})


app.listen(port, () => {
    console.log(`Example app listening at http://localhost:${port}`)
})

export { app};

This is my jest tests:

import request from 'supertest'

describe('test cases', () => {
    const mockTestFunction =  jest.fn()

    beforeEach(() => {
        jest.clearAllMocks() // <---------- it doesn't help to clear
        jest.restoreAllMocks()
        mockTestFunction.mockClear()
        mockTestFunction.mockRestore()
    })

    it('1',   async () => {
        jest.mock('../util', () => ({
            testFunction:  mockTestFunction
        }))

        mockTestFunction.mockReturnValue('test 1')

        const {app} = await import('../expressApp')

        return request(app)
            .get(`/`)
            .expect(200)
            .then((response) => {})
    })

    it('2',  async () => {

        const {app} = await import('../expressApp')

        return request(app)
            .get(`/`)
            .expect(200)
            .then((response) => {}) // here I always get mocked "test 1"
    })
})

My purpose is clear mockTestFunction for test "2", but as a result, I get always

"'test 1 result of testFunction'", it mocked it first test case and I can't restore it. I want to restore mockTestFunction to original (non-mocked) implementation, it should return "'result of testFunction'"

from Jest clear mocks between test cases (javascript)