https://gist.github.com/davetron5000/a8e10d842d51adab8444ecce421a5f64
This is trickier as it has some very convoluted code in it, and the “eternal?" concept, which I find confusing. Assuming this is a domain concept devs would know, I wouldn't bother testing it as it's trivial.
I also would not test precision with dates/times because it almost always doesn't matter and can be a huge pain to maintian.
https://ruby.social/@lucian/113078463709054465