A Test of Mettle (The Iron Druid Chronicles #3.1) by Kevin Hearne published 2 December 2011
This wee story, told from Granuaile’s point of view, takes place concurrently with the events of HAMMERED, book three of The Iron Druid Chronicles. 

Connected to but separate from Hammered, A Test of Mettle is a nice palate cleanser. In the main series Granuaile MacTiernan, is a delightful smart young woman who’s driven. Here though, it seems like she’s on something. During that first paragraphe when I realize it was her – because I didn’t read the description – I thought “Is she high?” She didn’t seem like the woman in the main series but that could be because of Atticus’ point of view. However, it was interesting to see the different trials in the making of a druid. Apparently it’s not reading books for 12 years.

You can read it for FREE here