Comment by hinkley | Hacker News Reader

Comment by hinkley | Hacker News Reader

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> go with end-to-end tests

I've found that E2E tests make for a pretty bad case of hill-climbing where tests are concerned. To the point where I think that's the pathology of the testing icecream cone.

It's easier conceptually go to 'up' the testing tree from unit tests to E2E tests, than it is to come down. People do what they are most familiar with, and if the E2E tests are first, then they are the most familiar. They are also glitchy as hell, and I see disdain for that get applied to all tests, not just the human tragedy that Selenium turned out to be. Also the ways in which unit test habits are considered 'bad' in functional tests are either less consequential or easier to walk away from. I'm not entirely sure which it is, or if it's both, but it's definitely less painful to relearn.

We also overvalue the E2E test versus human testing. I can't count how many times someone has come to tell me a login button is broken, 20 minutes before the E2E tests fail and tell me the same thing. Computers arbitrating code regressions are half the point of CI, so if your tests aren't arbitrating, they aren't doing their job, and should be fired.

E2E have higher capex and lower opex - hard to set up well, cheap to maintain if you do.

Low level tests are the reverse - easy to get started, hard to maintain.

If youve got a really well oiled framework e2e tests are spectacular but getting to that point can vary between easy and "harder than the actual project itself" and if you half ass it (which most people do) it ends up a useless flaky mess.

> cheap to maintain if you do.

I've only seen this with projects in maintenance mode. Any major functionality changes tend to land teeth-first in the E2E tests, and after a few cycles of that you start dragging your feet a bit on major changes. E2E tests tend to lock in assumptions about the structure of your application, not just the minutia (which is not without its own set of problems).

It is more difficult to get people to write maintainable E2E tests than it is getting them to write maintainable application code, so I've retreated and retrenched.

Weird Ive always found the opposite - E2E tests tend to make the fewest assumptions about the way the application is built.

In most cases we could literally rewrite the whole app in a different language and barely change the tests.

E2E tests do require a solid infrastructure though. If you have tooling problems you cant fix (e.g. you hit selenium's dark corners way too frequently because your web app is even a bit quirky) then maintainence cost can quite quickly exceed any benefit you derive.

Ive also hit this problem of "Id have to create my own equivalent of selenium for interacting with this app's interface" a few times and yeah, the required engineering effort to do it well explodes to the point where its just not worth it.

> It's easier conceptually go to 'up' the testing tree from unit tests to E2E tests, than it is to come down.

It all depends on the language and the project, but my experience is usually the opposite. It's often much easier to write an end to end test. To be able to write a unit test you usually have to architect the code to make it easy to mock, etc - and that takes significant skill for most real world projects.

E2E tests have a lot of downsides, but being challenging to write is probably not one of them.

I took it as: if you only have E2E tests then retrofitting unit tests is hard.

My experience agrees with this. Adding unit tests to untestable code (think: class has 10 dependencies that it news up being the first branching of a depdendecy graph to be untangled) requires refactors that just don’t get done with the busyness of other priorities.

> I took it as: if you only have E2E tests then retrofitting unit tests is hard.

That's been my experience. My point is that the reason the project has E2E tests and not unit tests is because it was easier to add E2E tests.

Yea, you definitely don't want people writing e2e tests because it's easier than writing other tests or because there aren't any other tests.

I’m aware of all the problems that e2e tests have, and yet I find it more useful to have 1 test that adds something to a basket and 1 test that removes it than 100 unit tests without contract tests (which I never got the hang of TBH).

(To be fair, my projects are low on JavaScript which somewhat changes the trade-off calculations, but I haven’t seen any assertions about project types above.)

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