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2.1.0 • Public • Published

eight-track Build status

Record and playback HTTP requests

This is built to make testing against third party services a breeze. No longer will your test suite fail because an external service is down.

eight-track is inspired by cassette and vcr

Getting Started

Install the module with: npm install eight-track

// Start up a basic applciation
var express = require('express');
var eightTrack = require('eight-track');
var request = require('request');
express().use(function (req, res) {
  res.send('Hello World!');
// Create a server using a `eight-track` middleware to the original
  url: 'http://localhost:1337',
  fixtureDir: 'directory/to/save/responses'
// Hits original server, triggering a `console.log('Pinged!')` and 'Hello World!' response
request('http://localhost:1338/', console.log);
// Hits saved response but still receieves 'Hello World!' response
request('http://localhost:1338/', console.log);


eight-track exposes eightTrack as its module.exports.


Middleware creator for new eightTrack's. This is not a constructor.

  • options Object - Container for parameters
    • url String|Object - URL of a server to proxy to
      • If it is a string, it should be the base URL of a server
      • If it is an object, it should be parameters for url.format
    • fixtureDir String - Path to load/save HTTP responses
      • Files will be saved with the format {{method}}_{{encodedUrl}}_{{hashOfRequestContent}}.json
      • An example filename is GET_%2F_658e61f2a6b2f1ae4c127e53f28dfecd.json
    • normalizeFn Function - Function to adjust request's save location signature
      • If you would like to make two requests resolve from the same response file, this is how.
      • The function signature should be function (info) and can either mutate the info or return a fresh object
      • info will have the following properties
        • httpVersion String - HTTP version received from request (e.g. 1.0, 1.1)
        • headers Object - Headers received by request
        • trailers Object - Trailers received by request
        • method String - HTTP method that was used (e.g. GET, POST)
        • url String - Pathname that request arrived from
        • body Buffer - Buffered body that was written to request
      • Existing normalizeFn libraries (e.g. multipart/form-data can be found below)

eightTrack returns a middleware with the signature function (req, res)

// Example of string url
  url: 'http://localhost:1337',
  fixtureDir: 'directory/to/save/responses'
// Example of object url
  url: {
    protocol: 'http:',
    hostname: 'localhost',
    port: 1337
  fixtureDir: 'directory/to/save/responses'

If you need to buffer the data before passing it off to eight-track that is supported as well. The requirement is that you record the data as a Buffer or String to req.body.

normalizeFn libraries

eightTrack.forwardRequest(req, cb)

Forward an incoming HTTP request in a mikeal/request-like format.

  • req http.IncomingMessage - Inbound request to an HTTP server (e.g. from http.createServer)
  • cb Function - Callback function with (err, res, body) signature
    • err Error - HTTP error if any occurred (e.g. ECONNREFUSED)
    • res Object - Container that looks like an HTTP object but simiplified due to saving to disk
      • httpVersion String - HTTP version received from external server response (e.g. 1.0, 1.1)
      • headers Object - Headers received by response
      • trailers Object - Trailers received by response
      • statusCode Number - Status code received from external server response
      • body Buffer - Buffered body that was written to response
    • body Buffer - Sugar variable for res.body


Proxy server with subpath

eight-track can talk to servers that are behind a specific path

// Start up a server that echoes our path
express().use(function (req, res) {
// Create a server using a `eight-track` middleware to the original
  url: 'http://localhost:1337/hello',
  fixtureDir: 'directory/to/save/responses'
// Logs `/hello/world`, concatenated result of `/hello` and `/world` pathss
request('http://localhost:1338/world', console.log);


In lieu of a formal styleguide, take care to maintain the existing coding style. Add unit tests for any new or changed functionality. Lint via grunt and test via npm test.


Copyright (c) 2014 Uber

Licensed under the MIT license.


npm i eight-track

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