<TEST> is a special Level exclusive to the Steam version of BIT.TRIP BEAT, serving as a cross promotion for the then-upcoming Portal 2 game. It is a unique level consisting of only one very long and moderately difficult stage. It uses the soundfont of DESCENT for its Beats. The song featured is Science is Fun from the Portal 2 trailers. Unlike the other Levels, which run for nearly 15 minutes each, <TEST> only clocks in around 2 and a half minutes in length. It also lacks the MEGA MODE entirely, only featuring HYPER and NETHER.
The background is an animated scene from Aperture Laboratories from Portal 2 with GLaDOS observing the player's progress, and the paddle has been altered to resemble a minimalist Portal Gun (or possibly a Sentry Turret). The status bars are gone entirely, preventing the player from tracking how well they're doing. Additionally, the Score and Multiplier numbers frequently flicker back and forth between the BIT.TRIP font and the Portal 2 font.
The stage lacks any Orange or Blue Beats, instead featuring the standard Yellow ones, albeit recoloured light orange and blue and given matching trails in reference to the colours of the two portals in the Portal games, alongside Pale Yellow Beats, which keep their characteristic delay, as well as Navy Green Beats, which move in erratic patterns as if they were moving through portals themselves. The final part of the Level is capped off by a large conglomerate of Linked Beats, whose links form the Aperture Laboratories logo.