* * * * *
                                        
             To unit test or not to unit test, that is the question
                                        
> There are two parts of your code. Code that can be unit tested and code
> that can't be unit tested.
> 
> Code that can't be unit tested is simple. Any code that has to touch IO
> (Input/Output) can't be unit tested. Period. Any code that doesn't touch IO
> can be unit tested. It's that simple.
> 
> … 
> 
> Keep ALL IO segregated from the rest of your code. Keep IO functions and
> methods super small. Do not inject IO polluted objects into other parts of
> your code.
> 

“Nothing should ever be mocked. Period. If you don't agree you likely don't
under... | Hacker News [1]”

In hindsight, this is obvious. The issue I have with unit testing projects
like “Project: Lumbergh [2],” “Project: Sippy-Cup [3]” or “Project: Cleese
[4]” is that they're nearly all IO with very little logic (with the caveat
that “Project: Lumbergh” implements all the business logic interspaced with
IO).

With that said, even though the author also stated not to mock at all, I do.
We have a few network services that “Project: Lumbergh” relies upon, and I
have written my own versions of those services that basically respond with a
canned answer for a particular query. It was easy since the services speak a
common protocol (DNS (Domain Name System) in this case) and I don't have to
implement the logic of those services to determine the answer.

I also decided to implement a new regression test and keep the one I have
working [5] as a separate test. This way, it'll be easier to implement tests
like “data source B replies, data source A times out.” I'm also keeping each
test in its own file, so adding new ones should be way easier and hopefully,
we won't end up with another 16,000 tests [6].

[1] https://news.ycombinator.com/item?id=27733397
[2] gopher://gopher.conman.org/0Phlog:2018/09/11.2
[3] gopher://gopher.conman.org/0Phlog:2014/03/05.1
[4] gopher://gopher.conman.org/0Phlog:2018/09/11.2
[5] gopher://gopher.conman.org/0Phlog:2021/07/01.1
[6] gopher://gopher.conman.org/0Phlog:2021/06/10.2
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Discussions about this page

Re: To unit test or not to unit test, that is the question [ 2021-07-08 ]
  gemini://marginalia.nu/log/02-re-tests.gmi

Email Sean Conner at sean@conman.org

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