I can see why the `to_a` is necessary with your current implementation.  However, I think it would be better to `include Enumerable` (and define an `each` to delegate to the wrapped `formatters` array) -- then no `to_a` would be needed here and it would preserve the existing enumerable interface of `RSpec.configuration.formatters`.  (I suspect some users may rely on it being an array-like/enumerable object as well).