MRI on a Mac refers to Mac Resource Inspector and the test includes: This test is done on any MacBook 2015 upwards as well as any iMac Mac Mini or Mac Pro units.

Audio: Presence Test
Battery Condition: Combined Battery Test and Presence Test
Bluetooth Presence Test
Camera: Presence Test
Display Test includes:
Presence Test for the Display as well as Black Light Controller
Display Serial Number Format test
EDID Checksum Test
Fault Detection TestFan Test: High Speed Test and Low Speed test
Graphics: Video Controller Presence Test

Memory Tests are quite thorough and include the following checks:
Address as Data Test
Bit Checkerboard Test
DIMM Match verification test
Knaizuk Hartmann Test
SMBIOS Verification Test BANK 0/DIMM0
SMBIOS verification Test BANK 1/DIMM0

MLB Tests include the following:App Code Mode Test
Checksum Test
Descripto Mode on Test
EPM CV UV Configuration ID Test
Event Buffer Retrieval
L1 Cache Test management Engine Presence Test
MLB Serial Number Test
Sensor Check Test

Power Port:
Presence Test
Middle Pin Test

SD Card Reader:
Presence Test
Sensors: Temperature check all around the entire unit including trackpad palm rest and airflow. We also check the Voltage throughout the unit to ensure the unit is functioning correctly from an electronic perspective.

Storage: Presence Test
System: Recovery Partition Presence Test

Device Detention Test
Link Width Verification Test

Wifi: Presence Test