AI makes tech debt more expensive

> Companies with relatively young, high-quality codebases benefit the most from generative AI tools, while companies with gnarly, legacy codebases will struggle to adopt them. In other words, the penalty for having a ‘high-debt’ codebase is now larger than ever.

This mirrors my experience using LLMs on personal projects. They can provide good advice only to the extent that your project stays within the bounds of well-known patterns. As soon as your codebase gets a little bit "weird" (ie trying to do anything novel and interesting), the model chokes, starts hallucinating, and makes your job considerably harder.

Put another way, LLMs make the easy stuff easier, but royally screws up the hard stuff. The gap does appear to be widening, not shrinking. They work best where we need them the least.

The niche I've found for LLMs is for implementing individual functions and unit tests. I'll define an interface and a return (or a test name and expectation) and say "this is what I want this to do", and let the LLM take the first crack at it. Limiting the bounds of the problem to be solved does a pretty good job of at least scaffolding something out that I can then take to completion. I almost never end up taking the LLM's autocompletion at face value, but having it written out to review and tweak does save substantial amounts of time.

The other use case is targeted code review/improvement. "Suggest how I could improve this" fills a niche which is currently filled by linters, but can be more flexible and robust. It has its place.

The fundamental problem with LLMs is that they follow patterns, rather than doing any actual reasoning. This is essentially the observation made by the article; AI coding tools do a great job of following examples, but their usefulness is limited to the degree to which the problem to be solved maps to a followable example.

Can't tell you how much I love it for testing, it's basically the only thing I use it for. I now have a test suite that can rebuild my entire app from the ground up locally, and works in the cloud as well. It's a huge motivator actually to write a piece of code with the reward being the ability to send it to the LLM to create some tests and then seeing a nice stream of green checkmarks.

It's containerized and I have a script that takes care of everything from the ground up :) I've tested this on multiple OS' and friends computers. I'm thankful to old me for writing a readme for current me lol.

>Please tell me this is satire.

No. I started doing TDD. It's fun to think about a piece of functionality, write out some tests, and then slowly make it pass. Removes a lot of cognitive load for me and serves as a micro todo. It's also nice that when you're working and think of something to add, you can just write out a quick test for it and add it to kanban later.

I can't tell you how many times I've worked on projects that are gigantic in complexity and don't do any testing, or use typescript, or both. You're always like 25% paranoid about everything you do and it's the worst.

>It's a huge motivator actually to write a piece of code with the reward being the ability to send it to the LLM to create some tests and then seeing a nice stream of green checkmarks.

Yeah that’s not TDD.

Don't you have a book to get to writing instead of leaving useless comments? Haha.

More importantly I have a French cleat wall to finish, a Christmas present to make for my wife, and a toddler and infant to keep from killing themselves.

But I also have a day job and I can’t even begin to imagine how much extra work someone doing “TDD” by writing a function and then fixing it in place with a whole suite of generated tests would cause me.

I’m fine with TDD. I do it myself fairly often. I also go back in and delete the tests that I used to build it that aren’t actually going to be useful a year from now.

Like I said above, I like the ability to scaffold tests using english and tweaking from there. I'm still not sure what point you're trying to make.

Your original point was that it was great to “write some code then send it to the LLM to create tests.”

That’s not test driven development.