tern-qunit provides a tern plugin for QUnit.

After installing and converting your project as Tern Project, go at Tern project property, click on Tern / Modules item and select the QUnit tern plugin (ECMAScript tern plugin must be selected too) :

Completion

After that you can benefit with QUnit completion :

Completion for assert is available too :

Web Browser

You can play with online demo which uses CodeMirror (inside Web Browser).