junit was not invented, it was a port from Smalltalk's SUnit, which was created on 1989, ~6 years before the first release of Apache. Yes, the extreme programming (XP) craze hadn't popularized TDD, but united testing as a practice already existed, even if only some communities.

Though I agree, that although not a technical justification, an explanation as to why there are no tests is because Apache HTTP is from the 90's. Not writing unit tests was par for course back then. Most FLOSS code bases in the 90s didn't have unit tests, let a alone a CI to run the test suite for each change. Adding tests later is hard. Though there are some tests under the test folder.

Now I learned something. Seems like I am not old enough