Function update

packages/react-reconciler/src/__tests__/ReactNewContext-test.js:1467–1476

(key, value)

    const UPDATE = 'UPDATE';
    function update(key, value) {
      return {
        type: UPDATE,
        key,
        value,
        toString() {
          return `update('${key}', ${value})`;
        },
      };
    }

    function randomInteger(min, max) {
      min = Math.ceil(min);