Hacker News Reader

Comment by magicalhippo | Hacker News Reader

I think it depends on what exactly the code does.

We have some custom rounding routines (to ensure consistent results). That's the kind of stuff you want to have lots and lots of unit tests for, testing all the paths, edge cases and so on.

We also have a complex price calculation module, which depends on lots of tables stored in the DB as well as some fixed logic to do its job. Sure we could test all the individual pieces of code, but like Lego pieces it's how you put them together that matters so IMO integration testing is more useful.

So we do a mix. We have low-level unit testing for low-level library style code, and focus more on integration testing for higher-level modules and business logic.

View on HN

I take a similar approach in .NET. I try to build these Lego pieces as traditional classes - no dependencies (except maybe a logger), just inputs and outputs. And then I have a few key "services" which tie everything together. So the service will pull some data from an API and maybe pull some data from an API, then pass it to these pure classes for processing.

I don't unit test the service, I integration test the api itself which indirectly tests the service. Mock the third party API, spin up a real db with testcontainers.

And then I unit test the pure classes. This makes it much easier to test the logic itself, and the service doesn't really have any logic - it just calls a method to get some data, then another method to process it and then returns it. I could quite easily use mocks to test that it calls the right methods with the right parameters etc, but the integration tests test that stuff implicitly, without being a hindrance to refactoring and similar work.

This is of course the correct answer - it depends on the context of your code. A single dogmatic approach to testing will not work equally well across all problem domains.

Simple stateless components, hitting a defined wire protocol or file format, utilizing certain API’s, testing numerical stuff, implies unit testing will go far.

Stateful components, complex multi-class flows, and heavily data driven domains will often benefit from higher level integration/end to end tests.

I just wrote a sibling comment and then realized you just stated exactly the same I wanted to say, but with more concrete examples :)

That's exactly the sweet spot: complex, self-contained logic units might benefit from low-level unit testing, but for the most part, what you're interested to know is if the whole thing works or not. Just IMHO, of course...

Reply on news.ycombinator.com