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oh-see Build Status

So that you can see how OC components look in production before publishing them to production.

Oh-see is a wrapper for mirror-mirror which is a wrapper for Nightmare.js. Oh-see is been built for:

  • Opening a matrix of urls and viewports with Chrome
  • Optionally specify a set of operations to perform
  • Take a screenshot
  • Replace a component's baseUrl and re-render it
  • Optionally specify another set of operations to perform
  • Take another screenshot
  • Compare the screenshots and save a diff file with the highlighted differences

Most important features:

  • Crazy quick compare to Selenium with Phantom
  • Able to hide/show Browser
  • Works with any OS
  • Able to use DevTools and do debugging with Chrome


  • Node version: min: 6
  • <oc-component> container needs to be present in rendered components to make oh-see work.


npm install oh-see

Usage example

const OhSee = require('oh-see');
const oh = OhSee({
  // Nightmare.js options 
  openDevTools: true,
  show: false
  concurrency: 5,
  timeout: 20000,
  debug: true,
  componentName: 'a-component',
  urls: {
    com_home: '',
    com_search: '',
    com_product: ''
  transformation: {
    type: 'replaceBaseUrl',
    newUrl: 'http://localhost:3030/',
    oldUrl: ''
  screenshotsPath: './screenshots'
});, result) => {


  1. Set up an instance
  2. Configure the runner
  1. Start the runner

Set up an instance

var ohSee = new OhSee([NighmareOptions]);

Look at Nighmare.js options.

Configure the runner


This is an object with the following structure:

name type mandatory description
componentName string yes The component name
concurrency number no Default 3, is the concurrency of tests
cookies object no Allows to specify cookies to be used for each request
debug boolean no When true, shows stuff in the console
headers object no Allows to specify headers to be used for each request
preRendering array of functions no An array of nightmareJs actions to perform before the first screenshots. Look at the example below
postRendering array of functions no An array of nightmareJs actions to perform after the transformation and before the second screenshots. Look at the example below
retries number no Default 3, number of retries after a failing session
screenshotsPath string yes The path where to save the screenshots
timeout number no Default 20000, when the session is going to be restarted
transformation object yes The transformation to apply to the component. Look at the Transformation types below
tryAppendLang boolean no Default false, when true appends to the component's href the __ocAcceptLanguage parameter, inheriting the value from html DOM element's lang attribute. This is required when re-rendering a server-side rendered component that depends on Accept-Language attribute for being rendered in the correct language
urls object yes The urls to test. Key is used to generate screenshots file name so keep it simple and without spaces and stuff
viewports array of arrays no Default [[800, 600]], the viewports for executing the tests

Nightmare actions example

This example shows how to make a screenshot with a menu opened, assuming the transformation replaces the menu and then needs to run another javascript initialisation and then wait to complete before performing the same action again.

  preRender: [
    (nightmare) => nightmare.evaluate(() => $('#navbar-button').click()
  postRender: [
    (nightmare) => nightmare.evaluate(() => {
      window.menusReady = false;
      window.menus.initialise(() => window.menusReady = true);
    (nightmare) => nightmare.wait(() => window.menusReady === true),
    (nightmare) => nightmare.evaluate(() => $('#navbar-button').click())

Transformation types

Base url replacement

Replaces the components' base url to another one. Useful for comparing a local one with the production one.

const transformation = {
  type: 'replaceBaseUrl',
  oldUrl: '',
  newUrl: 'http://localhost:3000/'

Start the runner;

Where callback is going to have an error and/or a response with the results. If any of the requests fails, the callback will include both an error + the response with succeeding screenshot links.


Yes please. Open an issue first.