This comports quite well with my personal experience. In late 1999 I happened to pick up XP Explained and set about to try this testing thing. At the time, there wasn't any "Unit Tests == Fast Tests" thing. What we did on our project was have two different types of tests: "Fast" tests and "SlowAndExpensive" tests, that we ran separately. But there wasn't much some fundamental distinction between them. That came a lot later.