Typescript: Null и Undefined

import { expect, test } from 'vitest'
import formatPrice from './index';

test('formatPrice', () => {
  expect(formatPrice()).toBe('$0.00');
  expect(formatPrice(null)).toBe('$0.00');
  expect(formatPrice(200)).toBe('$200.00');
  expect(formatPrice(3.145)).toBe('$3.15');
});