Riven/tests/README.md

Tests are divided up by region. This is because tests cannot share state, and therefore cannot share the rate limiting done within a RiotApi instance. However, rate limiting is separate for each region, so it is safe to send requests to different regions from different instances.

The tests within an individual file do share their RiotApi instance thanks to custom test runners and some macros I hacked together which are located in async_tests.rs. They are set up in a way to look like normal test output for fun and probably to confuse people.