Function looksNative

tests/js/quint.js:50–53

(fn)

    throw new Error(`'${fn}' does not throw`);
  },
  looksNative(fn)
  {
    if (!fn.toString().includes('[native code]')) throw new Error(`'${fn}' does not look native`);
  },
  enumerable(obj, propertyName)
  {
    const descriptor = Object.getOwnPropertyDescriptor(obj, propertyName);