cy-dom-diff

cy-dom-diff allows matching chunks of DOM against HTML; including dynamic content.

Introduction

cy-dom-diff consist of two parts. First is a Cypress command that matches a DOM element against a regular expression. When a DOM element is matched its HTML is normalized to produce consistent diffable output while maintaining sematic meaning. This includes:

• whitespace and newlines are normalized
• tags and attributes are printed on individual lines
• comments are removed
• tags and attributes can be ignored through configuration

In the second part cy-dom-diff provides a template function to generate a regular expression from a HTML string. This HTML string is passed through the same normalization as the DOM element (described above) as well as allowing embedded regular expression for dynamic content.

Installation and Setup

npm install --save-dev @swimlane/cy-dom-diff

Import the Cypress commands in cypress/support/index.js or cypress/support/commands.js

import '@swimlane/cy-dom-diff/commands';

Usage

In a basic example the following will assert that the element matches the regexp generated by the dom template tag. Most of the HTML string within the tagged template string is treated literally. However, regular expressions within the embedded expression are matches as expected.

import { dom } from '@swimlane/cy-dom-diff';

const TIME = /\d?\d:\d?\d\:\d?\d/;
const NUMBER = /[\+\-]?\d*\.?\d+(?:[Ee][\+\-]?\d+)?/;

cy.get('#clock').domMatch(dom`
    <span>The current time is:</span>
    <span class="clock">${TIME} ${/[AP]/}M</span>
    <span class="offset">${NUMBER}</span> hrs
  `);

cy.domMatch Cypress command

cy.domMatch will run the domMatch assertions (see below) and add a Cypress runner log with a diff.

cy.domDiff Cypress command

cy.domDiff is used in the same way as cy.domMatch but will only add a Cypress runner log with a diff. It will not fail if the DOM does not match and will not retry.

domMatch Chai assertion

At its lowest level cy-dom-diff adds a Chai assertion for matching the DOM. This will not generate a Cypress log except to show that the assertion passed or failed. Use cy.domMatch to get better logging.

import { dom } from '@swimlane/cy-dom-diff';

const TIME = /\d?\d:\d?\d\:\d?\d/;
const NUMBER = /[\+\-]?\d*\.?\d+(?:[Ee][\+\-]?\d+)?/;

cy.get('#clock').should('domMatch', dom`
  <span>The current time is:</span>
  <span class="clock">${TIME} ${/[AP]/}M</span>
  <span class="offset">${NUMBER}</span> hrs
`);

// OR

cy.get('#clock').then($el => {
  expect($el).to.domMatch(dom`
    <span>The current time is:</span>
    <span class="clock">${TIME} ${/[AP]/}M</span>
    <span class="offset">${NUMBER}</span> hrs
  `);
});

Credits

cy-dom-diff is a Swimlane open-source project; we believe in giving back to the open-source community by sharing some of the projects we build for our application. Swimlane is an automated cyber security operations and incident response platform that enables cyber security teams to leverage threat intelligence, speed up incident response and automate security operations.