not sure what you're point is here. It sounds similar to "we use to use blood letting and leeches and doctors didn't clean their hands and everything was fine so what are you getting at?"

Good tests have real benefits. The fact that people shipped without them in the past in no way suggests they aren't needed or have no point.

Are you getting older? A lot of people anchor their intuition of time and history to a certain year. There are probably still lots of people who think the 1990s is not that long ago even though it’s now over a quarter century since it ended. Maybe you mentally default to 2012 or so, when it might be true that most popular software shipped without automated tests (although manual QA was a lot more extensive in 1992).

But 20 years ago is now 2006, and unit tests were well established as a best practice. Perl had extensive automated tests in the late 1990s that everyone who ever compiled Perl would have noticed, since they were run by default and produced obvious output. Kent Beck’s “Test Driven Development: By Example” was released in 2002, and popularized both the name and practice.

I agree with the spirit of what you wrote, but my recollection of the timeline is different. The first decade of the 2000s was peak Crazy Agile Advocacy, but IIRC it wasn’t until the 2010s that unit testing really became almost universal practice. Much before that and it was still tangled up with XP, TDD and lots of other things that certainly weren’t universally accepted as good practices (notwithstanding the strident advocacy of a certain group of consultants/authors/speakers/bloggers and their fans).

I remember, back in the mid-2000s, when we had some consultants brought in to talk about different aspects of quality and testing. There were several working groups, each led by one of those external consultants, and one of them was about unit testing. This was in a relatively large software development organisation for the time, a few thousand people, and while some parts of the organisation had some form of automated testing operating by then, it definitely was not the case that the well-known products produced by the organisation all had a unit test suite. Other practices we’d consider routine today, such as peer code reviews, were also in their infancy during that period: some were doing them, many were not, and generally we had much less experience of how to do them effectively than we have today.

As an industry, I don’t think we really matured in how even the most ardent fans of unit testing were writing test suites until the 2010s either. In the 2000s, we still had lots of people mocking the entire universe and then writing unit tests that were 99% testing those mocks because of 100% test coverage requirements, and similar dogmatic nonsense.

By the 2020s, I think there was much more awareness of that automated testing is generally a good idea, but there are different kinds/levels of automated testing and finding a mix that suits each project’s specific needs is important. One of the great benefits from the more recent AI tools, particularly the agentic ones over the past year or so, has been that it has clearly demonstrated both the value of a good automated test strategy and how much of a waste of time vacuous tests are.

Not really, but I can see why some people think that.

We treat 100% test coverage as "required, but by itself not sufficient". It doesn't give us false confidence that everything will be perfect or anything like that. But it provides us with the discipline to make sure no corners are cut, and the bugs that are fixed don't come back.

One refreshing aspect was that during PR reviews we stopped debating whether something needed test coverage. Instead we focused on what was being tested and how.

I’d be curious to know what percentage of the time spent implementing tests would have otherwise gone to discussions about whether to implement them or not. ;)

Not really?

About 20 years ago, I was working on Firefox and we had millions of tests on CI. I was working on a host of other open source apps and they all had tests (most of them had no CI, of course).

However, what actually happens is that careless drivers often cripple or kill innocent bystanders in other vehicles as a result of their poor driving. That's why seatbelt laws and improved vehicle safety features are a good thing.