https://uxdesign.cc/how-to-test-readability-40d4f0f00c8f
Leverage your design today with this lean readability testing technique.
What in my practice turns out to be more practical (and faster) is to test how readable is the particular font that goes with branding of the particular brand you design for and appears on the given screen ratios.
What influences readability of text
Apart from the choice of font, there are several factors that can improve or decrease readability. Among these are primarily:
font weight
font size
leading (something that is also called line height)
line width
justification
color of text
case usage (capitalized or lower-case letters)
Of course, apart from the mentioned elements the content itself