After all my researches, i could not find an answer to my problem.

As i try to mock busboy in my project using jest, it keeps on saying that `mockImplementation` (and `mockRestore`) is not a function

```
import * as Busboy from 'busboy';

jest.mock('busboy');
describe('Sample test', () => {
  const mockedEvenMap = {};

  beforeAll(() => {
    Busboy.mockImplementation(() => {
      return { // mock `on` event of Busby instance
        on: (event, callback) => {
          mockedEvenMap[event] = callback;
        },
      };
    });

  });

  afterAll(() => {
    Busboy.mockRestore();
  });
}

```

Busboy exports its constructor as a default value of the module, but the mock does not seem to be applied.

*busboy index.d.ts*

```
declare module 'busboy' {
    const temp: busboy.BusboyConstructor;
    export = temp;
}

```

*Jest version 24.9*

*Busboy version 0.3.1*

any idea?