RE: [PATCH] t/t7704-repack-cruft.sh: avoid failures during long-running tests

[<rsbecker@nexbridge.com>]

On Monday, August 5, 2024 3:37 PM, Taylor Blau wrote:
>On systems where running t7704.09 takes longer than 10 seconds, the test can fail.
>
>The test works by doing the following:
>
>  - First write three unreachable objects, backdating the mtime for a
>    single object ($foo) which we expect to prune.
>
>  - Repack the repository into a pack containing reachable objects, and
>    another three cruft packs, each containing one of the objects
>    written in the previous step.
>
>  - Backdate the mtimes of the cruft pack *.mtimes files themselves.
>    (Note that this does not affect what is pruned further down in the
>    test, but is done to ensure that the cruft packs are rewritten
>    during that step).
>
>  - Then repack with --cruft-expiration=10.seconds.ago, expecting to
>    prune one of the three unreachable objects written in the first
>    step.
>
>  - Assert that the surviving cruft packs were rewritten, object $foo is
>    pruned, and unreachable objects $bar, and $baz remain in the
>    repository.
>
>If longer than 10 seconds pass between writing the three unreachable objects (the
>first step) and the "git repack --cruft" (the fourth step), we will mistakenly prune
>more objects than expected, causing the test to fail.
>
>The $foo object which we expect to prune has its mtime set back to
>10,000 seconds relative to the current time, but we prune it with a cutoff of
>10.seconds.ago.
>
>Instead, set the cutoff to be 1,000 seconds to give the test much longer time to run
>without failing. This helps platforms where running individual tests can perform
>slowly, on my machine this test runs much more quickly:
>
>    $ hyperfine './t7704-repack-cruft.sh --run=9'
>    Benchmark 1: ./t7704-repack-cruft.sh --run=9
>      Time (mean ± σ):     647.4 ms ±  30.7 ms    [User: 528.5 ms, System: 124.1 ms]
>      Range (min … max):   594.1 ms … 696.5 ms    10 runs
>
>Reported-by: Randall Becker <randall.becker@nexbridge.com>
>Signed-off-by: Taylor Blau <me@ttaylorr.com>
>---
> t/t7704-repack-cruft.sh | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
>diff --git a/t/t7704-repack-cruft.sh b/t/t7704-repack-cruft.sh index
>71e1ef3a10..959e6e2648 100755
>--- a/t/t7704-repack-cruft.sh
>+++ b/t/t7704-repack-cruft.sh
>@@ -330,7 +330,7 @@ test_expect_success '--max-cruft-size with pruning' '
> 		# repack (and prune) with a --max-cruft-size to ensure
> 		# that we appropriately split the resulting set of packs
> 		git repack -d --cruft --max-cruft-size=1M \
>-			--cruft-expiration=10.seconds.ago &&
>+			--cruft-expiration=1000.seconds.ago &&
> 		ls $packdir/pack-*.mtimes | sort >cruft.after &&
>
> 		for cruft in $(cat cruft.after)
>
>base-commit: 406f326d271e0bacecdb00425422c5fa3f314930
>--
>2.46.0.46.g406f326d27.dirty

LGTM. Thank you.