TIL about Elixir's System.unique_integer/1

TIL about System.unique_integer/1, which guarantees you an integer that it hasn’t (yet) handed out in the current runtime. 😍

Pass in [:positive, :monotonic] as the argument to get a unique, increasing number—useful for ordering in tests to know at a glance that one entity was created before another:

user1 =
  AccountsFixtures.user_fixture(%{
    email: "u#{System.unique_integer([:positive, :monotonic])}@example.com"
  })

user2 =
  AccountsFixtures.user_fixture(%{
    email: "u#{System.unique_integer([:positive, :monotonic])}@example.com"
  })

(I’d started writing my own GenServer to do this, but gave up quickly trying to handle a bunch of edge cases. 😅)