As discussed in the "Testing Your Code" twiki (section: "Asynchronous Tests")

> When testing asynchronous functionality use test.wait()/test.resume(fn) instead of test.wait(resumeFn, arbitraryTimeout) where possible. 

One way to handle this would be to execute `this.wait()` at the  bottom of the test (without arguments), and execute `this.resume(fn)` inside of a `Y.later`.  An example of this can be found in the [IO unit tests](https://github.com/yui/yui3/blob/master/src/io/tests/unit/js/upload-iframe-tests.js#L41).