Hi @ollien and welcome!
You should be able to turn off tzdata automatic updates in your tests by setting:
config :tzdata, :autoupdate, :disabled
in your test.exs config (GitHub - lau/tzdata: tzdata for Elixir. Born from the Calendar library. · GitHub)
Btw: you can now do time zone conversions directly in Elixir with the tzdata library without Timex: GitHub - lau/tzdata: tzdata for Elixir. Born from the Calendar library. · GitHub
