There is exactly zero problem bringing up a container for integration tests in Elixir as well, there’s nothing special about it, it’s still Docker + Compose in the end. 
As for Kafka, I believe Overview — brod v4.5.5 is the accepted way of doing it. It also has integration with GitHub - elixir-broadway/broadway: Concurrent and multi-stage data ingestion and data processing with Elixir · GitHub.
