How to stub fs.readFile functions

stubfs.js

const fs = require('fs')

function readFile (filename) {
  if (fs.existsSync(filename)) {
    return fs.readFileSync(filename, 'utf8')
  }
  throw new Error('Cannot find file ' + filename)
}

describe('mocking individual fs sync methods', () => {
  const sinon = require('sinon')

  beforeEach(() => {
    sinon.stub(fs, 'existsSync').withArgs('foo.txt').returns(true)
    sinon
      .stub(fs, 'readFileSync')
      .withArgs('foo.txt', 'utf8')
      .returns('fake text')
  })

  afterEach(() => {
    // restore individual methods
    fs.existsSync.restore()
    fs.readFileSync.restore()
  })

  it('reads non-existent file', () => {
    console.assert(readFile('foo.txt') === 'fake text')
  })
})

Hey, what if i have a simple function getFile(path) that returns the file,
and i want to test fs.readFileSync where it throws an error?
What I have is :

it('should throw an error id fs.readFileSync throws an error', () => {
const error = new Error("some err message")
const stub = sinon.stub(fs, readFileSync)
stub.throws(error)
)}

try {
stub ();
} catch (error) {
expect(stub).to.throw(error)

the test passes, but it does not print the error message, does not seem to execute the code.