Re: [PATCH v2 1/3] diff-highlight: add some tests.

[Brian Henderson <henderson.bj@gmail.com>]

On Fri, Aug 19, 2016 at 10:51:23AM -0400, Jeff King wrote:
> On Fri, Aug 19, 2016 at 07:42:35AM -0700, Brian Henderson wrote:
> 
> > > > +# PERL is required, but assumed to be present, although not necessarily modern
> > > > +# some tests require 5.8
> > > > +test_expect_success PERL 'name' 'true'
> > > 
> > > If the platform lacks PERL prerequisite, this will simply be
> > > skipped, and if the platform has it, it will always succeed.
> > > 
> > > I am not sure what you are trying to achieve by having this line
> > > here.
> > 
> > I originally didn't have this line, and my comment was referring to the
> > t/README which says
> > 
> >    Even without the PERL prerequisite, tests can assume there is a
> >    usable perl interpreter at $PERL_PATH, though it need not be
> >    particularly modern.
> > 
> > There is current functionality in diff-highlight which requires at least
> > perl 5.8 (the utf8 functions). I was going to add a test for this as
> > well, but I'm not super comfy with multibyte chars.
> 
> Yeah, I'd agree this test would want the PERL prereq. It is not just
> using perl for one-liners in support of the script; it is testing major
> perl functionality that should be skipped if we do not have a modern
> perl available.
> 
> > Eric recommended adding this line, what do you think?
> > 
> > would `test_set_prereq PERL` be better?
> 
> test_set_prereq is for telling the test scripts that we _have_ perl, but
> what I think this script wants to do is test "do we have perl?" and
> abort otherwise. The way to do that is:
> 
>   if ! test_have_prereq PERL
>   then
> 	skip_all='skipping diff-highlight tests; perl not available'
> 	test_done
>   fi
> 
> > > > +test_expect_success 'diff-highlight does not highlight whole line' '
> > > > +	dh_test \
> > > > +		"aaa\nbbb\nccc\n" \
> > > > +		"aaa\n000\nccc\n"
> > > > +'
> > 
> > This (at least to me) is desired. See comment for `sub
> > is_pair_interesting`
> 
> Yeah, that is an intentional behavior, and makes sense to test.
> 
> > > > +test_expect_success 'diff-highlight does not highlight mismatched hunk size' '
> > > > +	dh_test \
> > > > +		"aaa\nbbb\n" \
> > > > +		"aaa\nb0b\nccc\n"
> > > > +'
> > 
> > This is undesired behavior, but currently implemented for simplicity,
> > see `sub show_hunk`
> > 
> > Do they need comments or something?
> 
> Undesired behavior should generally not be tested for. It just makes
> life harder for somebody when they make a change that violates it, and
> they have to figure out "oh, but it's _good_ that I changed that, the
> tests were wrong" (or more likely "I didn't fix it, but it's just broken
> in a different way, and neither is preferable").
> 
> If you want to document known shortcomings, the best thing to do is show
> what you'd _like_ to have happen, and mark it as test_expect_failure;
> the test scripts show this as a known-breakage, and somebody later who
> fixes it can flip the "failure" to "success".
> 
> -Peff

all very helpful, thanks!