“With humans, we were carrying this big history of regression tests and they were valuable. … If there is a regression test, AI will go and update that in a heartbeat. It won't even think twice.”
Maintainable · Hands-On Engineering Podcasts · October 2026
Moreira, who works on the formal specification language Quint, contrasting inherited human-written tests with AI-written ones. A human test usually exists because someone hit a real bug; an AI agent will rewrite it without hesitation to make its change pass.
Transcript
…in one part of the code base, I would have to completely redo the tests. And to get started, just understand what we are testing, right? What scenarios are we testing and which ones we're not testing? And then I can have confidence. But if I don't know what I'm testing, then they don't help me at
…me of being dropped in a project that I don't have a lot of experience in, that maybe some other humans wrote or I wrote 10 years ago. I'm like, what's going on? I don't know if I can trust everything the same way. Is that something kind of you're experiencing now? Does that kind of resonate?
…a regression test. I love regression tests. I think they're amazing. So I think with humans, we were carrying this big history of regression tests and they were valuable. And that's also the experience I have in the code base I've been working for a while. But then in this new one, it's like the tests are so empty. And if you go and look at them, they are also not really enforcing anything. If there is a regression test, AI will go and update that in a heartbeat. It won't even think twice. I don't know, it might think, I'm not sure. But I feel like it's just changing so much that I cannot keep track of it anymore. So I think it's very different. The AI-generated ones that generate tests just because, well, the humans that actually wrote those tests for some reason in the first place.
That makes a lot of sense. Well, I think before we go too much further, I think I want to give listeners some context about the type of work that you're doing. So I know you've spent several years now helping develop Quint, and you became, I believe, CEO earlier this year. For someone hearing about…
Quint is a specification language based on CLA, a formal specification language. We like to say it's an executable specification language now, because a lot of people are talking again about specifications like Markdown. So Quint is nothing like Markdown, right? Quint is code you can execute, but…
Interesting. Tell me, how does this, where does this, like, just to provide some context for myself and the listeners, if I'm, let's say, working on a web app, where does this kind of fit? If I'm running, if I'm working on, say, a Ruby on Rails app, would someone like a Ruby on Rails developer have…
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