.NET solution having 120+ projects, with 7000 tests of which maybe 1500 are integration and/or component tests.

Buid alone takes 4 minutes. Test suite heavily parallelized runs in about 2 to 3 minutes, infrastructure dependencies fully containerized using podman, no external API call.

And this is without mentioning the 5000 frontend tests (angular), including Playwright end-to-end tests wired to the backend (about 3 to 4 minutes run without the e2e tests).

And this is running on a dev machine with 64gb of RAM and an NVMe disk.

Some systems are just massive, and even if you run focused tests, it's easy for a change to have a large blast at least requiring a large rebuild, and at times to rerun a larger set of tests.

I've worked on projects where the test suite would take hours.