How to mock API functions inside saga with jest?

I want to mock API functions inside my saga tests but I couldn't because typescript complains that it's a read-only property. Here's my code.

// src/api/todos.ts
import axios from './utils/axios'
import { handleError } from './error'

export const fetchTodosApi = async () => {
   return axios.get(`/todos/`).catch(handleError)
}

I have index.ts that exports all API functions like so:

export { fetchTodosApi } from './todos'

Then my test saga:

// src/tests/fetchTodos
import { runSaga } from 'redux-saga'
import { fetchTodos } from 'sagas'
import * as api from 'api'

describe('testing fetchTodosApi ', () => {
   it('is able to fetch todos', async () => {
      const dispatchedActions: Array<any> = []
      api.fetchTodosApi = jest.fn(() => Promise.resolve({}))

      const fakeStore: any = {
         dispatch: (action: any) => dispatchedActions.push(action),
         getState: () => state,
      }

      await runSaga(fakeStore, fetchTodos, action).toPromise()

      expect(dispatchedActions[0].todos).toEqual({})

   })
})

The problem is I can't assign api.fetchTodosApi with a mock function cos it's a read-only property as per Typescript. If I change how api function are exported in index.ts in the api dir to something like:

import { fetchTodosApi } from './todos'
const api = { fetchTodosApi }
export default api

I can assign a mock function to api.fetchTodosApi but it retains its original definition, not from the mock function. How do I get around this? It works with vanilla Javascript as shown here: https://www.youtube.com/watch?v=a9f97afxa9A