You can mock the module like this:

import calculate from '../../calculate'
jest.mock('../xyz', ()=> () => Promise.resolve('mocked value'))

it('does something', async()=>{
  const op = await calculate()
  expect(op).toBe('mocked value')
})

if you need different return values from your mock you need to mock the module so it returns a spy. Then you have to import the module and you can set the return value during your tests:

import calculate from '../../calculate'
import myModule from '../xyz'
jest.mock('../xyz', ()=> jest.fn())

it('does something', async() => {
  myModule.mockImplementation(() => () =>  Promise.resolve('mocked value'))

  const op = calculate()
  expect(op).toBe('mocked value')
})

it('does something else', async() => {
  myModule.mockImplementation(() => () =>  Promise.resolve('another value'))
  const op = await calculate()
  expect(op).toBe('another value')
})


it('does fail', async() => {
  myModule.mockImplementation(() => () =>  Promise.reject('some Error')
  try{
    const op = await calculate()
  }catch (e){
    expect(e).toBe('some Error')
  }
})

Only methods can be spied. There is no way to spy on funcB if it's called directly like funcB() within same module.

In order for exported function to be spied or mocked, funcA and funcB should reside in different modules.

This allows to spy on funcB in transpiled ES module (module object is read-only in native ESM):

import { funcB } from './b';

export const funcA = () => {
    funcB()
}

Due to that module imports are representations of modules, this is transpiled to:

var _b = require('./b');

var funcA = exports.funcA = function funcA() {
    (0, _b.funcB)();
};

Where funcB method is tied to _b module object, so it's possible to spy on it.