Auto balancing 7 hours tests between 100 parallel jobs on CI – Buildkite example

Do you have large test suites in your company projects? How big are they? How do you deal with long running tests?

Probably keeping a few small projects with fast test suites instead of monolith would be a nice way but we all know it's not always that easy.

I'd like to build a client library for auto-balancing tests across CI nodes in other languages than Ruby and I'd love to learn what test runners tools you use in your favorite programming languages.