Csscomb.js
CSS coding style formatter
Spa Eye
Backbone debugger for Firefox
Protractor
E2E test framework for Angular apps
Blanket
blanket.js is a simple code coverage library for javascript. Designed to be easy to install and use, for both browser and nodejs.
Chai
BDD / TDD assertion framework for node.js and the browser that can be paired with any testing framework.
Rulers Guides.js
Creates Photoshop-like guides and rulers interface on a web page
Csscritic
A lightweight framework for regression testing of Cascading Style Sheets
Casper JS
Navigation scripting & testing utility for PhantomJS and SlimerJS
Framer
Modern Prototyping Tool
Bower
A package manager for the web, created at Twitter
Phantom Css
Visual/CSS regression testing with PhantomJS
Jquery Mockjax
The jQuery Mockjax Plugin provides a simple and extremely flexible interface for mocking or simulating ajax requests and responses
Punch
A fun and easy way to build modern websites
Sinon.js
Test spies, stubs and mocks for JavaScript.
JSHint
JSHint is a community-driven tool to detect errors in JavaScript code and enforce your team's coding conventions.
Should.js
BDD style assertions for node.js -- test framework agnostic
Intern
A next-generation code testing stack for JavaScript.