The conventions for Jest, in order of best to worst in my opinion:
src/file.test.jsmentioned first in the Getting Started docs, and is great for keeping tests (especially unit) easy to find next to source filessrc/__tests__/file.test.jslets you have multiple__tests__directories so tests are still near original files without cluttering the same directories__tests__/file.test.jsmore like older test frameworks that put all the tests in a separate directory; while Jest does support it, it’s not as easy to keep tests organized and discoverable
Since you don’t want 1, it sounds like 2 is your best option.