Some links to understand what accessibility testing is:

• Top Accessibility Testing Tools for Automation by Joe Colantonio
• Accessibility & Usability Testing Pathway by Katrina Clokie
• Understanding Accessibility Testing: Think like a Dweller, Not a Builder by Albert Gareev
• Malvoyance – vis ma vie numérique avec Marie-Françoise Pierre (FR)
• Protractor Accessibility Plugin by Marcy Sutton