Unlike all other vehicles it is a requirement for HGVs to have their brakes tested at least 4 times, one of these can include the MOT. The brakes are tested using a roller brake tester system from which a report is produced.
The report produced gives the transport manager not only detail on whether the brakes failed or passed but also goes into significant more detail which can assist on knowing whether the vehicle may need some repairs or remedial works to ensure the brakes are performing to their optimum level for the vehicle.
Brake efficiencies are included within the report detailing not only the performance of the brake disks and pads but also how the axels are performing and whether these may need to be attended to in order for the vehicle and brakes to perform at a safe and efficient standard.
The Driver and Vehicle Standards Agency (DVSA) have produced a helpful guide into understanding and getting the most out of your Brake Test Report. This can be found at on the government website at https://www.gov.uk/government/publications/understanding-your-hgv-or-trailers-brake-test-report