“…I can make the claim that TDD is for humans, not robots.” Ben Rady · Two's Complement
Hands-On Engineering Podcasts · September 2026
Rady is reporting the conclusion of a conference talk he gave, and he defends it in the same breath: he has tried many times to make agents work test-first, and says you can make them do it but the code does not come out better. He frames TDD as a design discipline whose whole value is the constraint it puts on a human writing the code. He then wonders aloud how many people will still be able to test-drive a codebase in twenty years.
Transcript
get out a file and I'm going to start filing these, you know. And that's
a file, not like a computer file, that is like a RASP.
Yeah, right. Exactly. A metal file. And I wonder if there's some future like this old code base on PBS where it's like, you know, we go in and we hand edit this code. One of the things that I said in the presentation that I did, like I was talking about, is that I think at this point I can make the claim, and others have made this claim too. And I don't think I'm alone here. I can make the claim that TDD is for humans, not robots. I have tried many, many times to build software using test-driven development with agents, and you can make them do it. I don't think it makes the code any better. I don't think it, because the why do you, why do we even do TDD? What was the point of TDD? Well, like, it was lots of things, but one of the goals was to make sure that you didn't wind up with untestable software, right? Like, you like the, because the problem with automated testing, oftentimes, people are like, well, it's really hard to write the tests because it just doesn't work. And it's like, yeah, because you didn't design it.
Yeah. You
didn't design it to be tested. Right. So the cure for that is, well, write the test first and then you can't help but design it to be tested because that's the only and most important constraint is right. Can I exercise this code to my test? I don't think that TDD is a human process. It's not an agentic process. And so it's the kind of thing where it's like 20 years from now, how many people are going to be able to like test drive out a code base? Like, I don't know, not very many. Maybe they'll have a show on, you know, BBC One where they're like, all right, I'm going to crack open my old editor here and we're going to go write some tests for this code base.
You're joking about this, but you do. I mean, like, you can see, well, you can't see, actually, the camera's not pointed down here. But like, I am surrounded by computers from the 1980s and 1990s that many people enjoy for exactly the reason that you're describing is like partly it's nostalgia, partly it's keeping something alive and understanding what's going on. But partly it's just I can explain everything that's going on in here. And I kind of like that.