BWG page 46 has the rules for how helpers earn tests for advancement, but I’m having trouble figuring out whether the tests are for the skill being used to help or the skill being helped.
For example: if my party member is making an Orienteering test & I help using my Navigation - do I earn a test for Navigation or Orienteering?
The wording “as if he had tested against the obstacle with his own ability” seems on a straightforward read to mean I get a test to advance or open my Orienteering. But the rule for helping with a stat on an unskilled test, “since he is helping with his stat, he earns a test for advancing his stat” seems like it might just as easily apply to helping with my Navigation, not Orienteering.
If one option was obviously more punishing I’d feel confident in the intent, but as it is I’m just not sure.
I’ve always read that as helpers taking a test for the ability they used to help (Navigation in your example), but can see how it could be read the other way
“As if he had tested against the obstacle with his own ability” seems on a straightforward read to mean you get a test to advance your Navigation; that is your own ability, after all.
I’m sure that’s how it works.
And remember, your character doing something in the fiction that uses their ability to help. Part of their advancement is the exercising of that ability, I think.
While the intent behind one rule isn’t automatically the intent behind another, @luke indicated the reason why a player can’t FoRK as part of an unskilled test because applying existing knowledge/muscle memory reinforces current patterns rather than learning new ones; so, it seems consistent that helping with a skill will advance that skill rather than provide insights into a different one.