global.process = { __proto__: process, pid: 123456 } Date.now = function () { return 1459875739796 } require('os').hostname = function () { return 'abcdefghijklmnopqr' } var pino = require(require.resolve('./../../../')) var log = pino({ prettyPrint: { errorProps: 'code,errno' } }) var err = Object.assign(new Error('kaboom'), { code: 'ENOENT', errno: 1 }) log.error(err)