Yes ExUnit is designed to isolate tests and test suites so you don’t get leakage and side effects between tests.
It even randomizes the order to help catch unintended dependencies and side effects to make testing robust.
You could use the test_helper compile time “evil” that @Hermanverschooten showed to create a globally fixed value.
You could also use many of the nicely explained flakey test approaches to undo all the goodness that ExUnit provides and make your tests flakey and evil too.
Such evil can include stashing a Req structure in the Application environment or Ets. So in your setup_all callback you try and get the Req struct and only create and set it if it is doesn’t yet exist.
You will likely introduce a race condition on the create which you thoughly deserve for doing such evil things.
I would just use setup_all to do the authentication once per test suite. How many test suites do you have?
Perhaps you need to think about Mocking?
