Test: form test needs update after the change to mark nodes dirty on a change event

As we were targeting all the gender radios for a change event, which meant we called change on the "m" one first, which caused an update, which didn't change the scope value as the "m" radio wasn't checked, and then updated the DOM from the scope, causing the "f" to be unchecked as the scope contained "m".
Comment to document what returning undefined from getValue means