Testing with users who have disabilities is a great complement to compliance standards like WCAG and Section 508. If you are aiming for a comprehensive approach, you want to include people with a range of disabilities, such as:
Vision Impairments
Blindness
Low vision
Color blindness
Hearing Impairments
Deafness
Hard of hearing
Motor (Physical) Disabilities
Limited dexterity (e.g., from arthritis, cerebral palsy)
Paralysis (e.g., quadriplegia, paraplegia)
Amputations or limb differences
Tremors (e.g., from Parkinsons disease)
Cognitive & Neurodevelopmental Disabilities
Dyslexia
ADHD
Autism spectrum disorder
Intellectual disabilities
Memory impairments (e.g., due to brain injury or dementia)
Speech Disabilities
Muteness (unable to speak)
Speech impairments (e.g., stuttering, dysarthria)
Neurological & Other Conditions
Epilepsy (sensitivity to flashing content)
Migraines triggered by visual stimuli