[jghn]

I didn't start my career until the late 90s but I never saw anyone write a unit test until the XP craze started kicking off in the early aughts. Even then it was a few more years before I saw it happen commonly.

[kazinator]

The fad of writing countless unit tests for every function, checking them in, and running them feverishly all the time, is what is new.

Programmers have tested individual low-level functions before using them to build higher level functions, since the dawn of programming.

Libraries with regression test suites existed long before TDD.

[jghn]

Sure, we had regression tests at my jobs back then but they were always written and managed by QA groups. I never saw nor wrote any until a few years later.