Re: [PATCH v7 1/6] t5323: test cases for git-pack-redundant

From: Junio C Hamano <gitster@pobox.com>
To: Jiang Xin <worldhello.net@gmail.com>
Cc: "Git List" <git@vger.kernel.org>,
	"SZEDER Gábor" <szeder.dev@gmail.com>,
	"Sun Chao" <sunchao9@huawei.com>,
	"Jiang Xin" <zhiyou.jx@alibaba-inc.com>
Subject: Re: [PATCH v7 1/6] t5323: test cases for git-pack-redundant
Date: Thu, 31 Jan 2019 13:44:29 -0800	[thread overview]
Message-ID: <xmqq7eek1ozm.fsf@gitster-ct.c.googlers.com> (raw)
In-Reply-To: 20190130114736.30357-2-worldhello.net@gmail.com

Jiang Xin <worldhello.net@gmail.com> writes:

> diff --git a/t/t5323-pack-redundant.sh b/t/t5323-pack-redundant.sh
> new file mode 100755
> index 0000000000..710fe9884c
> --- /dev/null
> +++ b/t/t5323-pack-redundant.sh
> @@ -0,0 +1,322 @@
> +#!/bin/sh
> +#
> +# Copyright (c) 2018 Jiang Xin
> +#
> +
> +test_description='git pack-redundant test'
> +
> +. ./test-lib.sh
> +
> +create_commits () {
> +	parent=
> +	for name in A B C D E F G H I J K L M N O P Q R
> +	do
> +		test_tick &&
> +		T=$(git write-tree) &&

Move this outside loop, not for efficiency but for clarity. This
helper function creates a single empty tree and bunch of commits
that hold the same empty tree, arranged as a single strand of
pearls.

By the way, I had to draw a table like this to figure out ...

     T A B C D E F G H I J K L M N O P Q R
1    x x x x x x x                       x
2        x x x x   x x x
3                x     x x x x x
4                        x x x x     x
5                  x x           x x
6                                x x   x
7                                    x x
8      x

... what is going on.  Perhaps something like this would help other
readers near the top of the file (or in test_description)?

> +format_packfiles () {
> +	sed \
> +		-e "s#.*/pack-\(.*\)\.idx#\1#" \
> +		-e "s#.*/pack-\(.*\)\.pack#\1#" |
> +	sort -u |
> +	while read p
> +	do
> +		if test -z "$(eval echo \${P$p})"
> +		then
> +			echo $p

All the "expected output" below will expect P$n:${P$n} prepared by
various create_pack_$n helpers we saw earlier, so an unknown
packfile would be detected as a line that this emits.  Is that the
idea?

> +		else
> +			eval echo "\${P$p}"
> +		fi
> +	done |
> +	sort
> +}
> +
> +test_expect_success 'setup master.git' '
> +	git init --bare master.git &&
> +	cd master.git &&
> +	create_commits
> +'

Everything below will be done inside master.git?  Avoid cd'ing
around in random places in the test script, as a failure in any of
the steps that does cd would start later tests in an unexpected
place, if you can.

> +test_expect_success 'no redundant for pack 1, 2, 3' '
> +	create_pack_1 && create_pack_2 && create_pack_3 &&
> +	git pack-redundant --all >out &&
> +	test_must_be_empty out
> +'
> +
> +test_expect_success 'create pack 4, 5' '
> +	create_pack_4 && create_pack_5
> +'
> +

> +cat >expected <<EOF
> +P2:$P2
> +EOF
> +
> +test_expect_success 'one of pack-2/pack-3 is redundant' '
> +	git pack-redundant --all >out &&
> +	format_packfiles <out >actual &&
> +	test_cmp expected actual
> +'

Do the preparation of file "expect" (most of the tests compare
'expect' vs 'actual', not 'expected') _inside_ the next test that
uses it.  i.e.

	test_expect_success 'with 1 4 and 5, either 2 or 3 can be omitted' '
		cat >expect <<-EOF &&
		P2:$P2
		EOF
		git pack-redundant --all >out &&
		format ... >actual &&
		test_cmp expect actual
	'

Again, I needed to draw this to see if the "one of ... is redundant"
in the title is a valid claim.  Something like it would help future
readers.

     T A B C D E F G H I J K L M N O P Q R
1245 x x x x x x x x x x x x x x x x     x
3                x     x x x x x

     T A B C D E F G H I J K L M N O P Q R
1345 x x x x x x x x x x x x x x x x     x
2        x x x x   x x x

I won't repeat the same for tests that appear later in this file,
but they share the same issue.

> +test_expect_success 'setup shared.git' '
> +	cd "$TRASH_DIRECTORY" &&
> +	git clone -q --mirror master.git shared.git &&

Why "-q"?

> +	cd shared.git &&
> +	printf "../../master.git/objects" >objects/info/alternates
> +'

Why not echo?  I recall designing the alternates file to be a plain
text file.  Is it necessary to leave the line incomplete?

> +test_expect_success 'remove redundant packs by alt-odb, no packs left' '
> +	git pack-redundant --all --alt-odb | xargs rm &&
> +	git fsck --no-progress &&

Why "--no-progress"?

> +	test_must_fail git pack-redundant --all --alt-odb >actual 2>&1 &&
> +	test_cmp expected actual
> +'
> +
> +create_commits_others () {
> +	parent=$(git rev-parse HEAD)

If this fails, you'd still go ahead and enter the loop, which is not
what you want.

> +	for name in X Y Z
> +	do
> +		test_tick &&
> +		T=$(git write-tree) &&

Lift this outside the loop.

> +		if test -z "$parent"
> +		then
> +			oid=$(echo $name | git commit-tree $T)
> +		else
> +			oid=$(echo $name | git commit-tree -p $parent $T)
> +		fi &&
> +		eval $name=$oid &&
> +		parent=$oid ||
> +		return 1
> +	done
> +	git update-ref refs/heads/master $Z
> +}