[caoilte]

Unit tests are just as important as integration tests as long as they're tightly scoped to business logic and aren't written just to improve coverage. Anything can be done badly, especially if it is quantified and used as a metric of success (Goodhart's law applies).

Integration tests can be just as bad in this regard. They can be flakey and take hours, give you a false sense of security and not even address the complexity of the business domain.

I've seen people argue against unit tests because they force you to decompose your system into discrete pieces. I hope that's not the core concern here becuase a well decomposed system is easier to maintain and extend as well as write unit tests for.

[bwfan123]

The problem with unit tests these days is that AI writes them entirely and does a great job at it. That defeats the purpose of unit tests in the first place since the human doesnt have the patience to review the reams of over-mocked test-code produced by AI.

The end-result of this are things like the code leak of claude code presumably caused by ai generated ci/cd packaging code nobody bothered to review since the attitude is: who reviews test or ci/cd code ? If they break big-deal, ai will fix it.

[senderista]

“Premature abstraction” forced by unit tests can make systems harder to maintain.

[jimbokun]

It can but more often it’s the opposite.

Code that’s hard to write tests for tends to be code that’s too tightly coupled and lacking proper interface boundaries.

[bluGill]

the problem is people make units too small. A unit is not an isolated class or function. (It can be but usually isn't) a unit is one of those boxes you see on those architecture diagrams.

[dpark]

Inability to unit test is usually either a symptom of poor system structure (e.g. components are inappropriately coupled) or an attempt to shoehorn testing into the wrong spot.

If you find yourself trying to test a piece of code and it’s an unreasonable effort, try moving up a level. The “unit” you’re testing might be the wrong granularity. If you can’t test a level up, then it’s probably that your code is bad and you don’t have units. You have a blob.