| >do you write tests for it? Or do you write tests for the higher level routines which call it? I think most write tests for the function. I try to not test things that are that simple. But I wouldn't fault anyone for writing a small number of test cases for it. >For example, in red-green-refactor TDD, you are not supposed to change the tests when you refactor.
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>What you've ended up with are tests for the specific structure, and not the general goals. I'm not familiar with this methodology. But if your refactoring requires changing the interfaces then it must require changing the tests. It may be ideal to have such rigid interfaces in some cases, but I don't think you have to be so committed to one methodology. Big changes require big testing. >If you write tests for the function then you hinder future refactoring from removeprefix(s, prefix) to s.removeprefix(prefix) once you switch to a Python which implements s.removeprefix (3.9, I think?) How? Is the old code supposed to stop working because a new function was added? You aren't obligated to delete perfectly working and tested code. And if the new version of Python breaks it somehow, the tests will tell you quickly compared to finding out in a bigger test. >Which is why I use coverage-based method to identify what need more tests. Coverage is a powerful tool, and easily misused. Coverage is fine. But I mean, coverage is for people who already committed to testing every line of code. Not every project has unit tests in the first place so coverage is a moot point. >The biggest problem is that you decide to not refactor because there are so many tests to delete, and you have to figure out if the failing test really is okay to delete (because it was implementation specific) vs. one that needs to be updated (eg, because it handles a regression case). This work is very easy compared to fixing the real product in most cases. If you didn't write a bunch of frivolous tests it isn't that much work. >>Those types of tests are not unit tests
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>Correct! And no one said they were. Well this is a discussion about unit tests. If you want to talk about other types of tests you need to be clear about that. >That's fine. You do you. I was just pointing out that unit tests are not always feasible to do. But I wish they were. The stuff I see at work was not designed by me, so it's not my fault it is infeasible to test at least. |
You aren't obligated to write unit tests either.
If your goal includes long-term maintainability then should refactor for simplicity and consistency. Removing unneeded code and unneeded tests is a good thing.
> coverage is for people who already committed to testing every line of code.
Much as I would like it, I don't have 100% coverage. I use coverage to identify and prioritize which areas of code need more tests. Some are more important than others.
I also use it to identify code which is no longer needed, like workarounds for third-party-package V2021 which have been fixed in late releases, and I have no need to support V2021 any more.
> If you didn't write a bunch of frivolous tests it isn't that much work.
My observation is that people write a bunch of frivolous tests.
> If you want to talk about other types of tests you need to be clear about that.
I am talking about how to design unit tests.
Someone else here pointed to Robert Martin's essay on exactly this topic, at http://blog.cleancoder.com/uncle-bob/2017/10/03/TestContrava... .
"Design the structure of your [unit] tests to be contra-variant with the structure of your production code. ... The structure of your tests should not be a mirror of the structure of your code."
The issue I'm describing is what Martin characterizes as "the Fragile Test Problem" with some unit test approaches.