marko/packages/runtime-class/test/__util__/async-helpers.js

exports.promiseProvider = async (delay, value) => {
  while (1 + delay--) {
    await immediatePromise();
  }
  if (value instanceof Error) {
    throw value;
  } else {
    return value;
  }
};

exports.callbackProvider = (delay, value) => {
  return function (callback) {
    exports.promiseProvider(delay, value).then(
      (resolved) => callback(null, resolved),
      (rejected) => callback(rejected),
    );
  };
};

exports.callbackProviderWithArgs = (delay, resolver = (x) => x) => {
  return function (...all) {
    const args = all.slice(0, all.length - 1);
    const callback = all[all.length - 1];
    const value = resolver(...args);
    exports.callbackProvider(delay, value)(callback);
  };
};

const immediate =
  typeof setImmediate === "undefined" ? setTimeout : setImmediate;
function immediatePromise() {
  return new Promise((resolve) => immediate(resolve));
}