Re: [PATCH v4 0/3] config: add '--sources' option to print the source of a config value

[Lars Schneider <larsxschneider@gmail.com>]

On 15 Feb 2016, at 19:05, Jeff King <peff@peff.net> wrote:

> On Mon, Feb 15, 2016 at 11:17:43AM +0100, larsxschneider@gmail.com wrote:
> 
>> I like the idea of a "test set up block" within a test script. In order
>> to clean up nicely before any subsequent tests I would like to propose
>> a "tear down" block. Would that work as a compromise in our "test cases
>> depend on earlier test cases" discussion?
> 
> I don't have any real problem with what you've written in the final
> patch, but I also don't think it's accomplishing much (and is more lines
> of code, and more running processes).
> 
> If you want to run test N without having run all of 1..N-1, what you
> really want is some known, reliable state when that test starts. But the
> tests before it do not necessarily know what that state is.  The best
> they can do is roughly restore the original state before they ran. But:
> 
>  1. What does the state consist of? Which files (and their contents)
>     are important to the test?
> 
>     In your tear-down you get rid of $INCLUDE_DIR, and you zero-out the
>     config files. But you leave expect, output, output.raw, and the
>     oddly named $CUSTOM_CONFIG_FILE. Nor do you clean up the
>     environment variables.
Good argument - I can't disagree.

> 
>     To be clear, I think it's perfectly fine to leave those. But you
>     are still making assumptions about what the next test relies on.
> 
>  2. We may create a clean slate, but that is probably not what the next
>     test wants. It will want to do its own setup. I.e., it will
>     probably not want a blank .git/config, and will create it itself,
>     just as you did in your setup step.
> 
> So rather than tearing down, I think we are better off trying to make
> tests themselves (or blocks of them) set up their own assumptions. E.g.,
> by overwriting files rather than appending to them. By using unique
> filenames, commit messages, etc for their tests. That's less of a big
> deal here, but in many tests that create commits, "test_commit foo"
> would fail a second time, because there are no changes to "foo". Doing
> "test_commit subdir/check-diff-in-subdir" is less likely to clash
> without another test.
> 
> Sometimes we _are_ better off with a teardown step, because subsequent
> tests would not reasonably think to clear some state we've set (e.g., in
> non-config tests, if we set some random config variable, we use
> test_config to tear it down afterwards rather than have each test clean
> out all of the config). So there's definitely a subjective judgement
> call on what is "reasonable" there. But I find it unlikely that your
> tear-down will help anybody in this case. Further tests will not care
> about $INCLUDE_DIR unless they reference it, and any further tests would
> set up their own .git/config, etc.

OK, I will remove the block in the next roll. Thanks for explaining
your thoughts on this.

- Lars