node/test/parallel/test-http-outgoing-internal-headers.js

// Flags: --expose-internals
'use strict';
const common = require('../common');
const assert = require('assert');

const { outHeadersKey } = require('internal/http');
const { OutgoingMessage } = require('http');

{
  // tests for _headers get method
  const outgoingMessage = new OutgoingMessage();
  outgoingMessage.getHeaders = common.mustCall();
  outgoingMessage._headers;
}

{
  // tests for _headers set method
  const outgoingMessage = new OutgoingMessage();
  outgoingMessage._headers = {
    host: 'risingstack.com',
    Origin: 'localhost'
  };

  assert.deepStrictEqual(outgoingMessage[outHeadersKey], {
    host: ['host', 'risingstack.com'],
    origin: ['Origin', 'localhost']
  });
}