Why does jest mock for mocking an import doesn't work when jest.mock is called inside a test suite?

I am not able to understand how imports work in unit tests with jest. I was trying to mock a hook exported from someFile

jest.mock('src/someFile', () => ({
  useFetch: () => ({ ... }),
}));

When it's written outside the described block, I am able to run the test as expected. However, moving the jest mock block inside the describe block or a test block doesn't work.

 describe('someHOC', () => {
  jest.mock('src/someFile', () => ({
      useFetch: () => ({ ... }),
    }));
   // Followed by tests
   });

Can someone suggest to me if we can make it work the same way with some changes, or is it not possible? Also, is __esModule: true, required in this case, why or why not?