Re: [PATCH v2 3/3] t: add -I<regex> tests

[Johannes Schindelin <Johannes.Schindelin@gmx.de>]

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Hi Michał,

On Tue, 13 Oct 2020, Michał Kępień wrote:

> > Hmm. I wonder whether we could do with a much more concise test script.
> > The test suite already takes a quite long time to run, which is not a
> > laughing matter: we had issues in the past where contributors would skip
> > running it because it took too long, and this test is sure to exacerbate
> > that problem.
>
> First, let me say that the goal of minimizing the run time of a test
> suite is close to my heart (it is an issue at my day job).  Yet, I
> assumed that this new test would not be detrimental to test suite run
> times as it takes about half a second to run t4069-diff-ignore-regex.sh
> on my machine - and (I hope) its contents are in line with the "tests
> are the best documentation" proverb.

Sadly, the test is not quite as fast on Windows. I just ran this (on a not
quite idle machine, admittedly) and it ended in this:

	# passed all 11 test(s)
	1..11

	real    0m51.470s
	user    0m0.046s
	sys     0m0.015s

Yes, that's almost a minute.

> > I could imagine, for example, that it would be plenty enough to do
> > something like this instead:
> >
> > -- snip --
> > diff --git a/t/t4013-diff-various.sh b/t/t4013-diff-various.sh
> > index 5c7b0122b4f..bf158be137f 100755
> > --- a/t/t4013-diff-various.sh
> > +++ b/t/t4013-diff-various.sh
> > @@ -6,6 +6,7 @@
> >  test_description='Various diff formatting options'
> >
> >  . ./test-lib.sh
> > +. "$TEST_DIRECTORY"/diff-lib.sh
> >
> >  test_expect_success setup '
> >
> > @@ -473,4 +474,24 @@ test_expect_success 'diff-tree --stdin with log formatting' '
> >  	test_cmp expect actual
> >  '
> >
> > +test_expect_success '-I<regex>' '
> > +	seq 50 >I.txt &&
> > +	sed -e "s/13/ten and three/" -e "/7\$/d" <I.txt >J.txt &&
> > +	test_must_fail git diff --no-index -I"ten.*e" -I"^[124-9]" I.txt J.txt >actual &&
> > +	cat >expect <<-\EOF &&
> > +	diff --git a/I.txt b/J.txt
> > +	--- a/I.txt
> > +	+++ b/J.txt
> > +	@@ -34,7 +31,6 @@
> > +	 34
> > +	 35
> > +	 36
> > +	-37
> > +	 38
> > +	 39
> > +	 40
> > +	EOF
> > +	compare_diff_patch expect actual
> > +'
> > +
> >  test_done
> > -- snap --
> >
> > Note how it tests various things in one go?
>
> Right, neat, though this does not (yet) test:
>
>   - the interaction between -I and --ignore-blank-lines (this is visible
>     in code coverage),

Right. Any chance you can finagle that in, e.g. by yet another `-e`
argument to the `sed` call?

>   - whether the list of hunks emitted varies for different -U<n> values,

I am not worried about that.

>   - diffstat with -I<regex>,

I am not worried about that, either, as `diffstat` consumes `xdiff`'s
output, therefore if one consumer works, another consumer will work, too.

>   - invalid regular expressions.

Right, that should be super easy (and quick) to test.

> Would you like me to add these tests to your proposal or to skip them,
> given that -I uses the same field for marking changes as ignored as
> --ignore-blank-lines does?

I'd say it depends how easily (read: in how small a test case or
modifications to an existing test case) you can add a test for that
interaction.

Thanks,
Dscho