Foreign Service Institute (FSI) language tests measure speaking and reading ability, with separate numerical scores for each. For example, 3/3 is usually the grade sought after completing FSI language training and usually adequate for work purposes. I've taken walk-in tests at FSI but don't know how they would measure the reading part through a phone conversation.

I wouldn't worry too much about "passing" the test because if it is an evaluation for job candidacy purposes then the objective is to measure actual language ability. The standard Arabic language training program for State employees consists of one year of intensive language training at FSI (more properly known as NFATC - National Foreign Affairs Training Center) in Arlington, Virginia, followed by a second year of intensive training in Tunis, Tunisia. Any candidate who has the ability to skip at least part of this training should have a benefit added to their ranking, although I am not sure exactly how this process works. (And the language incentive pay for "hard language" ability takes effect immediately after an employee scores a 3/3 on the relevant language.)