See issue tracker for 3.1.1 tickets.

• Limit all test suite selection operations to #qunit-fixture (see https://github.com/jquery/jquery/issues/2880)

• Check minified code for syntax errors (see https://github.com/jquery/jquery/issues/3075)

• Add CSS linter for test CSS to enforce our CSS styleguide.

• Potential use of new DOM/ES features , if they improve performance (e.g., gh-1868 and gh-1753)

  • Historically, new DOM/ES features have not been performant so we'll need to jsperf them and weigh against increased code size and complexity.
  • May need new API surface for things like .usedStyle and it may be master-only

• Improve modularity (e.g., gh-1864)

• Start using ES6 modules and transpile to other formats.

  • PEP has already started using ES6 modules: jquery/PEP#157
  • QUnit is next: jquery/qunit#707

• Improve support for "Web Components" features like ShadowRoot

  • See gh-1748, gh-1784, gh-1976.

• Reconcile invalid input behavior across the API. This is to be done in stages.

  • See gh-2134

• Add e2e tests.

  • focus tests - https://github.com/jquery/jquery/blob/a644101ed04d0beacea864ce805e0c4f86ba1cd1/test/unit/event.js#L2703, https://github.com/jquery/jquery/blob/a644101ed04d0beacea864ce805e0c4f86ba1cd1/test/unit/event.js#L2676

  • isDefaultPrevented, stopImmediatePropagation - https://github.com/jquery/jquery/blob/a644101ed04d0beacea864ce805e0c4f86ba1cd1/test/unit/event.js#L375

• Create a Web Download Builder

  • See gh-1691 for background.

• Add automated code coverage

  • See gh-1965 for background.

• Run unit tests with XHTML doctype

  • See gh-1731 for background.

• Drop Node.js <4 support in 2017

• Change code style for checking method presence

  • See gh-3221 for background

• Rewrite speed framework

• Explore simplification of jQuery.support

• Investigate possible unnecessary modularization of some variables

• Investigate possible reuse of support divs

  • See gh-2405 for background

• Standardize the way we check node disconnectedness

  • See gh-2404

• Reduce cyclomatic complexity of effects

• Reduce cyclomatic complexity of manipulation

• Investigate implementing jQuery (specifically .init) as an Array subclass

  • See gh-1754 for background

• Edge Focusin/out support (property missing on window)

  • See gh-2389

• FF to add focusin/out

  • FF issue