There are a couple of things you need to know if you want to have Flubaroo grade your Google form. When creating your Google form, choose Multiple Choice, Choose from List, or Checkboxes for the type of questions. Those work best with Flubaroo.
Now having said that, when I made my Spelling Test form, I chose "Text" as the question type. This DOES work with Flubaroo because there is only ONE correct way to spell the word. The students are only typing in that spelling word, so Flubaroo will grade it. Flubaroo is awesome for grading things that only have one correct answer. When I make Google forms that require explanations, I do not use Flubaroo to grade those.