I have the pleasure of speaking at the HaskellerZ meetup and at the Google office for an internal tech talk.
In these talks, I point to this page for the audience members to find more material on validity and validity-based testing.
I have written about Validity and Validity-based testing before.
The
validity
repository has a very thorough README that will walk you through an example and contains the motivation for the concepts and packages as well.The slide deck for the presentation is also available in that repository.