System tests too! The last code-base I worked on had do-everything system tests (with unexpectedly good coverage, I'll admit). They were so slow and passed of

System tests too! The last code-base I worked on had do-everything system tests (with unexpectedly good coverage, I'll admit). They were so slow and passed often enough that I didn't immediately spot flakiness. I got suspicious when the tests started failing regularly when I added new unrelated code.