When testing async code with QUnit, you currently need to execute a stop() at the start of your test function. See http://drupalcode.org/sandbox/ethanw/1438244.git/blob/refs/heads/7.x-1.x... for an example.

QUnit offers an asyncTest method for convenience working with tests of async code, see http://docs.jquery.com/QUnit/asyncTest. This is roughly equivalent to the above, but one advantage of having it integrated into the QUnit module is that async tests could be run subsequent to normal tests. Since async tests are, ironically, blocking, the would allow other tests to return their results more quickly, postponing the async testing till later.

Can we add an asyncTest: key to the test object used in Drupal.tests?

Happy to help with the code for this if it is a welcome feature.