WebdriverCSS

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Note: WebdriverCSS isn't yet compatible with WebdriverIO v3.0. We are currently working on it to make that happen soon. So stay tuned.

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CSS regression testing in WebdriverIO. This plugin is an automatic visual regression-testing tool for WebdriverIO. It was inspired by James Cryer's awesome project called PhantomCSS. After initialization it enhances a WebdriverIO instance with an additional command called webdrivercss and enables the possibility to save screenshots of specific parts of your application.

Never lose track of unwanted CSS changes:

How does it work?

1. Define areas within your application that should always look the same
2. Use WebdriverIO and WebdriverCSS to write some E2E tests and take screenshots of these areas
3. Continue working on your application or website
4. After a while rerun the tests
5. If desired areas differ from previous taken screenshots an image diff gets generated and you get notified in your tests

Example

var assert = require('assert');

// init WebdriverIO
var client = require('webdriverio').remote({desiredCapabilities:{browserName: 'chrome'}})
// init WebdriverCSS
require('webdrivercss').init(client);

client
    .init()
    .url('http://example.com')
    .webdrivercss('startpage',[
        {
            name: 'header',
            elem: '#header'
        }, {
            name: 'hero',
            elem: '//*[@id="hero"]/div[2]'
        }
    ], function(err, res) {
        assert.ifError(err);
        assert.ok(res.header[0].isWithinMisMatchTolerance);
        assert.ok(res.hero[0].isWithinMisMatchTolerance);
    })
    .end();

Install

WebdriverCSS uses GraphicsMagick for image processing. To install this package you'll need to have it preinstalled on your system.

Mac OS X using Homebrew

$ brew install graphicsmagick

Ubuntu using apt-get

$ sudo apt-get install graphicsmagick

Windows

Download and install executables for GraphicsMagick. Please make sure you install the right binaries desired for your system (32bit vs 64bit).

After these dependencies are installed you can install WebdriverCSS via NPM as usual:

$ npm install webdrivercss
$ npm install webdriverio # if not already installed

Setup

To use this plugin just call the init function and pass the desired WebdriverIO instance as parameter. Additionally you can define some options to configure the plugin. After that the webdrivercss command will be available only for this instance.

• screenshotRoot String ( default: ./webdrivercss )
  path where all screenshots get saved.

• failedComparisonsRoot String ( default: ./webdrivercss/diff )
  path where all screenshot diffs get saved.

• misMatchTolerance Number ( default: 0.05 )
  number between 0 and 100 that defines the degree of mismatch to consider two images as identical, increasing this value will decrease test coverage.

• screenWidth Numbers[] ( default: [] )
  if set, all screenshots will be taken in different screen widths (e.g. for responsive design tests)

• updateBaseline Boolean ( default: false )
  updates baseline images if comparison keeps failing.

Example

// create a WebdriverIO instance
var client = require('webdriverio').remote({
    desiredCapabilities: {
        browserName: 'phantomjs'
    }
}).init();

// initialise WebdriverCSS for `client` instance
require('webdrivercss').init(client, {
    // example options
    screenshotRoot: 'my-shots',
    failedComparisonsRoot: 'diffs',
    misMatchTolerance: 0.05,
    screenWidth: [320,480,640,1024]
});

Usage

WebdriverCSS enhances an WebdriverIO instance with an command called webdrivercss

client.webdrivercss('some_id', [{options}], callback);

It provides options that will help you to define your areas exactly and exclude parts that are unrelevant for design (e.g. content). Additionally it allows you to include the responsive design in your regression tests easily. The following options are available:

• name String (required)
  name of the captured element

• elem String
  only capture a specific DOM element, you can use all kinds of different WebdriverIO selector strategies here

• width Number
  define a fixed width for your screenshot

• height Number
  define a fixed height for your screenshot

• x Number
  take screenshot at an exact xy postion (requires width/height option)

• y Number
  take screenshot at an exact xy postion (requires width/height option)

• exclude String[]|Object[]
  exclude frequently changing parts of your screenshot, you can either pass all kinds of different WebdriverIO selector strategies that queries one or multiple elements or you can define x and y values which stretch a rectangle or polygon

• hide String[]
  hides all elements queried by all kinds of different WebdriverIO selector strategies (via visibility: hidden)

• remove String[]
  removes all elements queried by all kinds of different WebdriverIO selector strategies (via display: none)

• ignore String
  can be used to ignore color differences or differences caused by antialising artifacts in the screenshot comparison

The following paragraphs will give you a more detailed insight how to use these options properly.

Let your test fail when screenshots differ

When using this plugin you can decide how to handle design breaks. You can either just work with the captured screenshots or you could even break your integration test at this position. The following example shows how to handle design breaks within integration tests:

var assert = require('assert');

describe('my website should always look the same',function() {

    it('header should look the same',function(done) {
        client
            .url('http://www.example.org')
            .webdrivercss('header', {
                name: 'header',
                elem: '#header'
            }, function(err,res) {
                assert.ifError(err);

                // this will break the test if screenshot is not within the mismatch tolerance
                assert.ok(res.header[0].isWithinMisMatchTolerance);
            })
            .call(done);
    });

    // ...

The res variable will be an object containing details on the screenshots taken. It will have properties matching each element name, and the value of those properties will contain an array of screenshots at each resolution.

For example, the res object for the code above would be:

{ 
  header: [ 
    {
      baselinePath: 'webdrivercss/header.header.baseline.png',
      message: 'mismatch tolerance not exceeded (~0), baseline didn\'t change',
      misMatchPercentage: 0,
      isExactSameImage: true,
      isSameDimensions: true,
      isWithinMisMatchTolerance: true
    }
  ]
}

Applitools Eyes Support

Applitools Eyes is a comprehensive automated UI validation solution with really smart image matching algorithms that are unique in this area. As a cloud service it makes your regression tests available everywhere and accessible to everyone in your team, and its automated maintenance features simplify baseline maintenance.

In order to work with Applitools Eyes you need to sign up and obtain an API key. You can sign up for a free account here.

Applitools Eyes Example

var assert = require('assert');

// create a WebdriverIO instance
var client = require('webdriverio').remote({
    desiredCapabilities: {
        browserName: 'chrome'
    }
});

// initialise WebdriverCSS for `client` instance
require('webdrivercss').init(client, {
    key: '<your personal API key>'
});

client
    .init()
    .url('http://example.com')
    .webdrivercss('<app name>', {
        name: '<test name>',
        elem: '#someElement',
        // ...
    }, function(err, res) {
        assert.ifError(err);
        assert.equal(res.steps, res.strictMatches)
    })
    .end();

The following options might be interesting if you want to synchronize your taken images with an external API. Checkout the webdrivercss-adminpanel for more information on that.

• api String URL to API interface
• user String user name (only necessary if API requires Basic Authentication or oAuth)
• key String assigned user key (only necessary if API requires Basic Authentication or oAuth)

Define specific areas

The most powerful feature of WebdriverCSS is the possibility to define specific areas for your regression tests. When calling the command, WebdriverCSS will always take a screenshot of the whole website. After that it crops the image and creates a single copy for each element. If you want to capture multiple images on one page make sure you pass an array of options to the command. The screenshot capturing process can take a while depending on the document size of the website. Once you interact with the page by clicking on links, open layers or navigating to a new site you should call the webdrivercss command to take a new screenshot.

To query elements you want to capture you are able to choose all kinds of different WebdriverIO selector strategies or you can specify x/y coordinates to cover a more exact area.

client
    .url('http://github.com')
    .webdrivercss('githubform', {
        name: 'github-signup',
        elem: '#site-container > div.marketing-section.marketing-section-signup > div.container > form'
    });

Will capture the following:

Tip: do right click on the desired element, then click on Inspect Element, then hover over the desired element in DevTools, open the context menu and click on Copy CSS Path to get the exact CSS selector

The following example uses xy coordinates to capture a more exact area. You should also pass a screenWidth option to make sure that your xy parameters map perfect on the desired area.

client
    .url('http://github.com')
    .webdrivercss('headerbar', {
        name: 'headerbar',
        x: 110,
        y: 15,
        width: 980,
        height: 34,
        screenWidth: [1200]
    });

Exclude specific areas

Sometimes it is unavoidable that content gets captured and from time to time this content will change of course. This would break all tests. To prevent this you can determine areas, which will get covered in black and will not be considered anymore. Here is an example:

client
    .url('http://tumblr.com/themes')
    .webdrivercss('tumblrpage', {
        name: 'startpage',
        exclude: ['#theme_garden > div > section.carousel > div.carousel_slides',
                 '//*[@id="theme_garden"]/div/section[3]',
                 '//*[@id="theme_garden"]/div/section[4]']
        screenWidth: [1200]
    });

Instead of using a selector strategy you can also exclude areas by specifying xy values which form a rectangle.

client
    .url('http://tumblr.com/themes')
    .webdrivercss('tumblrpage', {
        name: 'startpage',
        exclude: [{
            x0: 100, y0: 100,
            x1: 300, y1: 200
        }],
        screenWidth: [1200]
    });

If your exclude object has more then two xy variables, it will try to form a polygon. This may be helpful if you like to exclude complex figures like:

client
    .url('http://tumblr.com/themes')
    .webdrivercss('polygon', {
        name: 'startpage',
        exclude: [{
            x0: 120, y0: 725,
            x1: 120, y1: 600,
            x2: 290, y2: 490,
            x3: 290, y3: 255,
            x4: 925, y4: 255,
            x5: 925, y5: 490,
            x6: 1080,y6: 600,
            x7: 1080,y7: 725
        }],
        screenWidth: [1200]
    });

Tweak the image comparison

If you experience problems with unstable comparison results you might want to try tweaking the algorithm. There are two options available: colors and antialiasing. colors might help you if you don't care about color differences on your page, while the antialiasing option can for example reduce unexpected differences on font or image edges:

client
    .url('http://tumblr.com/themes')
    .webdrivercss('tumblrpage', {
        name: 'startpage',
        ignore: 'antialiasing',
        screenWidth: [1200]
    });

Note: This doesn't affect the taken screenshots, but only the comparison calculations. By setting this option you reduce the sensitivity of the comparison algorithm. Though it's unlikely this might cause layout changes to remain unnoticed.

Keep an eye on mobile screen resolution

It is of course also important to check your design in multiple screen resolutions. By using the screenWidth option WebdriverCSS automatically resizes the browser for you. By adding the screen width to the file name WebdriverCSS makes sure that only shots with same width will be compared.

client
    .url('http://stephencaver.com/')
    .webdrivercss('startpage', {
        name: 'header',
        elem: '#masthead',
        screenWidth: [320,640,960]
    });

This will capture the following image at once:

file name: header.960px.png

file name: header.640px.png

file name: header.320px.png

Note that if you have multiple tests running one after the other, it is important to change the first argument passed to the webdrivercss() command to be unique, as WebdriverCSS saves time by remembering the name of previously captured screenshots.

// Example using Mocha
it('should check the first page',function(done) {
  client
    .init()
    .url('https://example.com')
    // Make this name unique.
    .webdrivercss('page1', [
      {
        name: 'test',
        screenWidth: [320,480,640,1024]
      }, {
        name: 'test_two',
        screenWidth: [444,666]
      }
    ])
    .end()
    .call(done);
});

it('should check the second page',function(done) {
  client
    // ...
    // Make this name unique.
    .webdrivercss('page2', [
      // ..
    ])
    // ...
);

Synchronize your taken Images

If you want to have your image repository available regardless where you run your tests, you can use an external API to store your shots. Therefor WebdriverCSS adds a sync function that downloads the repository as tarball and unzips it. After running your tests you can call this function again to zip the current state of your repository and upload it. Here is how this can look like:

// create a WebdriverIO instance
var client = require('webdriverio').remote({
    desiredCapabilities: {
        browserName: 'phantomjs'
    }
});

// initialise WebdriverCSS for `client` instance
require('webdrivercss').init(client, {
    screenshotRoot: 'myRegressionTests',

    // Provide the API route
    api: 'http://example.com/api/webdrivercss'
});

client
    .init()
    .sync() // downloads last uploaded tarball from http://example.com/api/webdrivercss/myRegressionTests.tar.gz
    .url('http://example.com')

    // do your regression tests
    // ...

    .sync() // zips your screenshot root and uploads it to http://example.com/api/webdrivercss via POST method
    .end();

This allows you to run your regression tests with the same taken shots again and again, no matter where your tests are executed. It also makes distributed testing possible. Regressions tests can be done not only by you but everyone else who has access to the API.

API Requirements

To implement such API you have to provide two routes for synchronization:

• [GET] /some/route/:file Should response the uploaded tarball (for example: /some/root/myProject.tar.gz) Content-Type: application/octet-stream
• [POST] /some/route Request contains zipped tarball that needs to be stored on the filesystem

If you don't want to implement this by yourself, there is already such an application prepared, checkout the webdriverio/webdrivercss-adminpanel project. It provides even a web interface for before/after comparison and stuff like this.

Contributing

Please fork, add specs, and send pull requests! In lieu of a formal styleguide, take care to maintain the existing coding style.

Default driver instance used for testing is PhantomJS (v1.9.8), so you need to either have it installed, or change the desiredCapabilities in the bootstrap.js file under the test folder to your preferred driver (e.g., Firefox).

You also need a web server to serve the "site" files and have the root folder set to "webdrivercss". We use the http-server package. To use this package, run these commands:

/path/to/webdrivercss-repo/ $ npm install -g http-server
/path/to/webdrivercss-repo/ $ http-server -p 8080

You can validate the site is loading correctly by visiting http://localhost:8080/test/site/index.html in a browser.

You'll also need a local selenium server running. You can install and start one via the following commands in a separate terminal:

npm install -g selenium-standalone
selenium-standalone install
selenium-standalone start