chai-modshot

visual regression testing plugin for chai. Uses modshot to create screenshots and compare them

How to use

Can be used with the should, expect or assert interfaces.

 
// 1. testing an HTML file for visual regression
var htmlFilePath = require.resolve('./index.html');
return expect(htmlFilePath).to.be.consistentWith('html-file-1');
 
// 2. testing a marko template for visual regression
var templatePath = require.resolve('./template.marko');
return expect(templatePath).to.be.consistentWith('marko-template-1');
 

Installation and Setup

Do an npm install chai-modshot to get up and running. Then use it for assertions.

 
var chai = require('chai');
var chaiModshot = require('chai-modshot');
 
chai.use(chaiModshot);
 

Configuring chai-modshot

chai-modshot can optionally be configured using a configure function as shown below. This should be done before the assertions. Also, configuring chai-modshot multiple times overrides the previous configurations.

require('chai-modshot').configure({
    outDir: 'shots/units',
    tolerance: 5,
    port: 4567,
    templateType: 'marko',
    lassoConfig: {
        plugins: [
            'lasso-less',
            'lasso-autoprefixer',
            'lasso-marko'
        ],
        'url-prefix': '/static',
        outputDir: 'static',
        fingerprintsEnabled: false,
        minify: false,
        bundlingEnabled: false,
        resolveCssUrls: true,
        cacheProfile: 'development'
    }
});
 

The .configure function takes an object with the below keys as parameter:

• outDir (Default: 'shots/units') the output directory for screenshots.
• tolerance (Default: 5) the percentage deviation with original screenshots upto which, the assertions should not fail.
• port (Default: 4567) the port to start the server on.
• templateType (Default: 'marko') the template engine that should be used. Currently, marko and html are supported
• lassoConfig the lasso configuration that should be passed to the template. The default configuration is as in the above example.

Assertions

consistentWith(useCase, selector, delay)

 
// 1. testing an HTML file for visual regression
var htmlFilePath = require.resolve('./index.html');
return expect(htmlFilePath).to.be.consistentWith('html-file-1', 'body', 1000);
 
// 2. testing a marko template for visual regression
var templatePath = require.resolve('./template.marko');
return expect(templatePath).to.be.consistentWith('marko-template-1');
 

Params

• useCase the prefix for the file name for the screenshot

• selector the css selector for the element to be checked for visual regression. Can be a string or an Array of selectors

• delay the number of milliseconds to wait before taking the screenshot.