TIL default parameters in Elixir that are function calls get re-evaluated every time you call the function.
This is how you’d hope this sort of thing works, but I think years of being burned by Python made me mistrust it.
Somehow I missed this my first time through the outstanding Testing Elixir by Andrea Leopardi and Jeffrey Matthias. Every time I open that book up I get something new and valuable.
This is a godsend for testability!