如何在JS单元测试中模拟静态变量？

function createCounter() {
  let count = 0;
  return function() {
    count++;
    return count;
  };
}

const counter = createCounter();
console.log(counter()); // 输出 1
console.log(counter()); // 输出 2

class Counter {
  static count = 0;

  static increment() {
    Counter.count++;
    return Counter.count;
  }
}

console.log(Counter.increment()); // 输出 1
console.log(Counter.increment()); // 输出 2

let count = 0;

function increment() {
  count++;
  return count;
}

export { increment };

import { increment } from './counter';

console.log(increment()); // 输出 1
console.log(increment()); // 输出 2