From: Jeff King <email@example.com> To: Stefan Beller <firstname.lastname@example.org> Cc: "Johannes Schindelin" <Johannes.Schindelin@gmx.de>, "Ævar Arnfjörð Bjarmason" <email@example.com>, git <firstname.lastname@example.org>, "Junio C Hamano" <email@example.com> Subject: Re: [PATCH 2/4] t5310: test delta reuse with bitmaps Date: Tue, 4 Sep 2018 16:02:25 -0400 [thread overview] Message-ID: <20180904200224.GB17481@sigill.intra.peff.net> (raw) In-Reply-To: <CAGZ79ka8e2-f4fYgy+=HUDdvugefvQ5TnDG0v8YmUn7kGhTdaQ@mail.gmail.com> On Tue, Sep 04, 2018 at 12:05:58PM -0700, Stefan Beller wrote: > Yeah, maybe we need to ask for more tests in the 'real' test suite, and not > just in some special corner (such as t/perf/ or any of the environment > variable proposals nearby). > > I wonder if we can make use of git.git in the test suite for similar things, > e.g. after reading the thread about "index corruption with git commit -p" , > I thought that we only have these toy examples in the test suite. Toy examples > show that the new feature barely works, and doesn't show it is working at scale. I think the toy examples do both. Often they drill down directly to a useful but rare corner case that _wouldn't_ be hit during normal operation. And being toys, they are a lot quicker to set up then trying to work with a 50MB repository. Take the "commit -p" one for example. It's not really about the repository shape but about a particular set of actions. If you don't test those actions, you won't reproduce the bug. > > There may be a larger lesson about tracking code coverage, but I don't > > know that most general code coverage tools would have helped (any > > overall percentage number would be too large to move). A tool that > > looked at the diff and said "of the N lines you added/touched, this > > percent is exercised in the test suite" might have been useful. > > From some offline discussion, maybe we want to adapt a philosophy of > > Each patch needs to add a test, that fails when the patch > is not applied, but succeeds when it is applied. This shows > that _some_ code in the patch is exercised at least. > > (and automatically/strongly enforce this going forwards; however > enforcing such a strict thing is hard, not sure how we'd do it.) I wouldn't want a hard-and-fast rule like that. If you're fixing a bug, sure, I think it's good to make sure it's exercised. And if you're adding a feature, you almost always add some basic tests (and almost certainly leave some corner without code coverage). But if you're writing an optimization, there's often no before/after test. Presumably it worked before, and hopefully it still works after, and it just got faster. You're generally relying on existing regression tests (from when that code was introduced) to save you from bugs. You might need to _write_ those tests if nobody did before. But it's hard to know without digging if there are decent tests or not. That's why I think code coverage of the lines in your diff is probably the best measure. -Peff
next prev parent reply other threads:[~2018-09-04 20:02 UTC|newest] Thread overview: 53+ messages / expand[flat|nested] mbox.gz Atom feed top 2018-08-21 18:41 [PATCH] test-tool.h: include git-compat-util.h Jeff King 2018-08-21 19:03 ` Junio C Hamano 2018-08-21 19:06 ` [PATCH 1/6] t/perf: factor boilerplate out of test_perf Jeff King 2018-08-21 19:06 ` [PATCH 2/6] t/perf: factor out percent calculations Jeff King 2018-08-21 19:06 ` [PATCH 3/6] t/perf: add infrastructure for measuring sizes Jeff King 2018-08-22 13:40 ` Derrick Stolee 2018-08-22 15:31 ` Jeff King 2018-08-21 19:06 ` [PATCH 4/6] t/perf: add perf tests for fetches from a bitmapped server Jeff King 2018-08-21 19:07 ` [PATCH 5/6] pack-bitmap: save "have" bitmap from walk Jeff King 2018-08-21 19:47 ` Derrick Stolee 2018-08-21 19:54 ` Jeff King 2018-08-31 15:23 ` Ævar Arnfjörð Bjarmason 2018-08-31 22:55 ` Jeff King 2018-09-01 7:41 ` [PATCH 0/4] un-breaking pack-objects with bitmaps Jeff King 2018-09-01 7:44 ` [PATCH 1/4] bitmap_has_sha1_in_uninteresting(): drop BUG check Jeff King 2018-09-01 7:48 ` [PATCH 2/4] t5310: test delta reuse with bitmaps Jeff King 2018-09-01 8:03 ` Jeff King 2018-09-01 20:29 ` Ævar Arnfjörð Bjarmason 2018-09-01 22:46 ` Ben Peart 2018-09-02 5:51 ` Jeff King 2018-09-04 19:05 ` Stefan Beller 2018-09-04 19:45 ` Junio C Hamano 2018-09-04 20:02 ` Jeff King [this message] 2018-09-01 7:49 ` [PATCH 3/4] traverse_bitmap_commit_list(): don't free result Jeff King 2018-09-01 7:50 ` [PATCH 4/4] pack-bitmap: drop "loaded" flag Jeff King 2018-09-04 19:30 ` [PATCH 0/4] un-breaking pack-objects with bitmaps Stefan Beller 2018-09-04 20:03 ` Jeff King 2018-09-08 6:43 ` Ævar Arnfjörð Bjarmason 2018-09-10 16:53 ` Junio C Hamano 2018-09-10 18:48 ` Jeff King 2018-09-10 19:23 ` Junio C Hamano 2018-08-21 19:07 ` [PATCH 6/6] pack-objects: reuse on-disk deltas for thin "have" objects Jeff King 2018-08-21 19:43 ` Junio C Hamano 2018-08-21 19:50 ` Junio C Hamano 2018-08-21 20:07 ` Jeff King 2018-08-21 20:14 ` Jeff King 2018-08-21 20:52 ` Junio C Hamano 2018-08-21 21:30 ` Jeff King 2018-08-21 20:57 ` Junio C Hamano 2018-08-21 21:32 ` Jeff King 2018-08-23 0:43 ` [PATCH 0/9] trailer-parsing false positives Jeff King 2018-08-23 0:44 ` [PATCH 1/9] trailer: use size_t for string offsets Jeff King 2018-08-23 0:45 ` [PATCH 2/9] trailer: use size_t for iterating trailer list Jeff King 2018-08-23 0:46 ` [PATCH 3/9] trailer: pass process_trailer_opts to trailer_info_get() Jeff King 2018-08-23 0:48 ` [PATCH 4/9] interpret-trailers: tighten check for "---" patch boundary Jeff King 2018-08-23 0:49 ` [PATCH 5/9] interpret-trailers: allow suppressing "---" divider Jeff King 2018-08-23 0:50 ` [PATCH 6/9] pretty, ref-filter: format %(trailers) with no_divider option Jeff King 2018-08-23 0:50 ` [PATCH 7/9] sequencer: ignore "---" divider when parsing trailers Jeff King 2018-08-23 0:50 ` [PATCH 8/9] append_signoff: use size_t for string offsets Jeff King 2018-08-23 0:51 ` [PATCH 9/9] sequencer: handle ignore_footer when parsing trailers Jeff King 2018-08-23 18:30 ` [PATCH 0/9] trailer-parsing false positives Junio C Hamano 2018-08-24 7:26 ` Jeff King 2018-08-21 20:00 ` [PATCH 6/6] pack-objects: reuse on-disk deltas for thin "have" objects Jeff King
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