The two lines 

      var suggestionToBeHighlighted = this._suggestionToBeHighlighted(idx);
      aria.utils.FireDomEvent.fireEvent('click', suggestionToBeHighlighted);

are repeating across the file, should be extracted as a local function, say `fireClickOnSuggestion(idx)`.

The repetition is small, but IMO it's always good to extract those kind of microfunctions in the test cases, first for code reuse and possibility to easily refactor it later, and second so that the main test case functions read well: `fireSomeEvent`, `checkSomething`, `checkSomethingElse`, `doSomeOtherAction`, `checkSomethingElse` instead of creating lots of messy variables. Those internal bookkeeping should be moved as much as possible in the methods called from the main method of the test case.