'use strict'; // Used to test the `uncaughtException` err object const assert = require('assert'); const { callbackify } = require('util'); { const sentinel = new Error(__filename); process.once('uncaughtException', (err) => { assert.notStrictEqual(err, sentinel); // Calling test will use `stdout` to assert value of `err.message` console.log(err.message); }); function fn() { return Promise.reject(sentinel); } const cbFn = callbackify(fn); cbFn((err, ret) => assert.ifError(err)); }