You write tests how I sometimes dream of writing tests, which is pure end-to-ends 
We’re still very similar in that I don’t write unit tests but I do test my contexts. My only experience with Phoenix has been full stack LiveView apps, and I like to keep a very strict boundary between MyApp and MyAppWeb. I consider them separate applications with a strict one-way dependency (except for MyAppWeb showing up in MyApp.Applcation’s supervisor) even though I have yet to add another client served by MyApp. TDDing my contexts also helps keep their design honest even though I’ll fully admit that there is a lot of CRUD that end up being largely being the same boilerplate tests, though these are not the types of tests that would be eliminated by types. Also, because there are exceptions to every rule, I do write some unit tests for utility functions usually in the form of a doctest. These often live in a separate namespace from MyApp or MyAppWeb since they are essentially library functions.
You got me there as I’ve actually totally written tests like that before. I’d feel icky about it and it led me to start only writing guards for control flow. My generally strategy in the past couple of years has been to ensure that all data has been cast to a known shape at the outer bounds, so these types of things shouldn’t happen. What I really should be doing on top of that is using property-based testing and I’m a little annoyed with myself that this thread has led to me exposing myself that I still don’t 
Do you think types make property-based tests redundant?
