Wikimedia Bugzilla is closed!

In no particular order:

* tests/js/fixtures.js and javascripts/application.js are loaded twice. Especially noticeable in debug mode. Please remove the redundant or use a utility module that both depend on instead of including the same file twice in two different modules. 

* fixtures.js is executing DOM functions without waiting for document ready, this can be a problem.

* If none of the MF tests are run (e.g. ?filter=jquery.colorUtil), then there should be no DOM manipulations or global variables/functions defined by MF unit test code. Schedule dom manipulation in teardown/setup functions, that way they are automatically reset after each test (so that they don't affect each other), and it also ensures none of them are ran if the tests aren't ran. Right now it creates the fixtures also if none of the tests are scheduled to run.

 And in debug mode it creates global variables MFE and MFET in some of the test files, these should be local to the suite, maybe use a closure for them like
( function ($, mw, MFConf, MFE, MFET) {
 /* .. */
}(jQuery, mediaWiki, mwMobileFrontendConfig, MobileFrontend, MobileFrontendTests));

.. Or, after porting to ResourceLoader, have them all under mw.*, where mw.conf and mw.messages are automatically reset after each test if you use (or build on) QUnit.newMwEnvironment().

* the "qunit-fixture-x" element is non-standard pollution of the document on Special:JavaScriptTest/qunit and isn't hidden by default. This causes it to be unconditionally and infinitely visible in plain sight on that page when only other test suites are ran (e.g. when setting ?filter=jquery.byteLength, the whole MobileFrontend fixture remains in plain sight.)

QUnit has build in fixture teardown/setup after each test, using the contents of <div id="qunit-fixture"> at time of the first test as base and resets it to that after each test. Use the QUnit "begin" (`QUnit.begin(fn callback)`) hook to add something to this (do not set innerHTML as that would break other test suites fixture code, instead append to it from the test initiator via the QUnit.begin() hook).

* This goes deeper into MobileFrontend's bigger issues, but it's using awfully generic names and titles all in the main namespace. Such as:
- global function `wm_toggle_section`
- DIV id="logo", "nav", "sq", "search", "anchor_1", "section_1"

* Assertions: The tests for addClass and removeClass should not be using hasClass for verification. Especially for the tests where it creates a new element and adds one class, it is more reliable to check the raw className property for equality instead. The hasClass assertions, similarly, should use className directly (or just as part of the '<div ..></div>' snippet) to create the test and then use hasClass to test it, right now it is mixing too much leaving a fair chance of missing failures if something is wrong with either one of them.