Tests are arranged into two categories, each in its own directory:
Conformance is defined at https://www.w3.org/TR/imsc-hrm/#conformance
Each IMSC document contains a short description of the IMSC HRM feature being tested.
All IMSC documents conform to the IMSC Text Profile.
The implementation report for the first edition of the IMSC HRM recommendation is at:
https://www.w3.org/wiki/TimedText/IMSC-HRM-1ED-Implementation-Report