MSLT (multiple sleep latency test)
A test in which you are given several short chances to sleep during the day and how quickly you fall asleep is measured.
A little more detail
After overnight polysomnography, five nap opportunities are given during the day, two hours apart; the first starts 1.5 to 3 hours after the end of the night recording. In each nap, the time to fall asleep and whether there is an early REM period are recorded. According to the AASM it is indicated in the evaluation of suspected narcolepsy and may be useful in idiopathic hypersomnia; it is not routinely used in the initial diagnosis of OSA or to assess change after CPAP. The maintenance of wakefulness test (MWT), in contrast, measures a person's ability to stay awake.
Source: Littner MR, Kushida C, Wise M et al. Practice parameters for clinical use of the multiple sleep latency test and the maintenance of wakefulness test. Sleep. 2005;28(1):113-121. doi:10.1093/sleep/28.1.113; Krahn LE, Arand DL, Avidan AY et al. Recommended protocols for the Multiple Sleep Latency Test and Maintenance of Wakefulness Test in adults: guidance from the American Academy of Sleep Medicine. J Clin Sleep Med. 2021;17(12):2489-2498. doi:10.5664/jcsm.9620