Check Using Simple Tester

WARNING: This page is about a different car, the 2005 Mitsubishi Montero. However, it is still accessible from the selected car via links, so may be relevant.

Depress the brake pedal repeatedly more than 40 times until the pedal depressing force feels heavy with the ignition switch at the "LOCK" (OFF) position to release the pressure of HBB power supply system.
Connect a pressure gauge and a pedal depression gauge as shown in the illustration and bleed air from the pressure gauge.
Perform the operation test without booster according to the following method.
Depress the brake pedal repeatedly more than 40 times with the ignition switch at "LOCK" (OFF) position to bleed pressure from the HBB power supply system. Measure the relation between the brake pedal depressing force and the hydraulic pressure.

Standard value:

Fig 1: Connecting Pressure Gauge And A Pedal Depression Gauge
Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.

Fig 2: Hydraulic Pressure Specification
Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
Perform the operation test with booster according to the following method.
Turn the ignition switch to the "ON" position and measure the relation between the brake pedal depressing force and the hydraulic pressure after pump motor was stopped.

Standard value:

Fig 3: Hydraulic Pressure Specification
Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.