I have started studying this book.
To make life easier here is the link to the examples:
http://www.adamtornhill.com/code/xrayexercises.html
So far I agree with the analysis. One minor niggle is the claim that small config files don’t need tests. That’s not true for say package.json.
My dependabot usage results in dependabot making 60 times as many commits as the next user. You really need a unit test for every feature that you use in a dependency. In the node world that can be painful.