Could I trouble you to test this with a few more verbs? I know there are no other Form III verbs in Lexicon, but you could add them in AllAraAbs (and linearise in AllAra) for testing purposes. Like this:

--# -path=.:../abstract:../common:prelude

abstract AllAraAbs = Lang, Extend ** {
  fun
    someTestVerb : V ;
    anotherTestVerb : V ;
    … }

and corresponding lins in AllAra.

The reason I'm asking: I was googling a bit, and found this page https://quizlet.com/204282015/arabic-masdar-rules-flash-cards/ which says

Form 3 المفاعلة Rule
Form III verbs and masdar have a distinctive alif. The verb يسافر does not use the regular masdar pattern. it is a rare exception for this form.

And that verb (s-f-r) is exactly the one in your unit test, so that makes me wonder whether removing the alif from the general constructor is the right thing to do.

It would be great to get more examples, preferably from all types here https://en.wiktionary.org/wiki/Category:Arabic_form-III_verbs (like sound, hollow, weak, geminate). If you are busy/prefer to do other things, I can also prepare the test suite and would appreciate if you could review it!