No, It is Immpossible. You should always write a new mock at the top of describe

You can use jest.mock() in the module scope of the test file. It will be hoisted to the top of the file before any import. Which means the imported module is already mocked. So that you can use mock.mockReturnValue() method in each test case to provide a different return value.

E.g.

index.js:

import someFn from './some-module';

export default function main() {
  return someFn();
}

some-module.js:

export default function someFn() {
  return 'a';
}

index.test.js:

import main from './';
import someFn from './some-module';

jest.mock('./some-module');

describe('71219584', () => {
  test('should pass 1', () => {
    someFn.mockReturnValue('fake a');
    console.log(main());
  });
  test('should pass 2', () => {
    someFn.mockReturnValue('fake b');
    console.log(main());
  });
});

Test result:

 PASS  stackoverflow/71219584/index.test.js
  71219584
    ✓ should pass 1 (17 ms)
    ✓ should pass 2 (2 ms)

  console.log
    fake a

      at Object.<anonymous> (stackoverflow/71219584/index.test.js:18:13)

  console.log
    fake b

      at Object.<anonymous> (stackoverflow/71219584/index.test.js:22:13)

Test Suites: 1 passed, 1 total
Tests:       2 passed, 2 total
Snapshots:   0 total
Time:        3.186 s