These organizations and open-source projects use QUnit to keep their code in check.
Discourse, discourse-subscriptions
Underscore.js, Backbone.js
formcore, layersnap, tablesaw
Vault, Vault, Nomad
KAS, structured.js
Hogan.js, twitter-text, Bootstrap
MediaWiki, VisualEditor, CSSJanus
WordPress
CefSharp
Ember.js, ember-qunit, ember-twiddle
ember-moment, ember-intl, ember-table
Globalize
jQuery, Sizzle, jQuery UI
jquery-validation, mockjax, inputmask
js-cookie
kiwix-js
Moment.js
Paper.js
StealJS, steal-qunit, steal-tools
three.js
Wikibase, data-model, data-values
ZeroClipboard