Re: [PATCH 4/7] parallel-checkout: add tests for basic operations

[Matheus Tavares Bernardino <matheus.bernardino@usp.br>]

On Fri, Apr 23, 2021 at 4:18 PM Derrick Stolee <stolee@gmail.com> wrote:
>
> On 4/22/2021 11:17 AM, Matheus Tavares wrote:
> > Add tests to populate the working tree during clone and checkout using
> > sequential and parallel mode, to confirm that they produce identical
> > results. Also test basic checkout mechanics, such as checking for
> > symlinks in the leading directories and the abidance to --force.
> >
> > Note: some helper functions are added to a common lib file which is only
> > included by t2080 for now. But they will also be used by other
> > parallel-checkout tests in the following patches.
> >
> > Original-patch-by: Jeff Hostetler <jeffhost@microsoft.com>
>
> Is this a standard thing? Or, did you change the patch significantly
> enough that "Co-authored-by:" is no longer appropriate?

No, I think "Co-authored-by" is appropriate, let's change this trailer :)

> > +++ b/t/lib-parallel-checkout.sh
> > @@ -0,0 +1,37 @@
> > +# Helpers for t208* tests
>
> I could see tests outside of the t208* range possibly having
> value in interacting with parallel checkout in the future.
>
> Perhaps:
>
>         # Helpers for tests invoking parallel-checkout

Will do!

> > +
> > +set_checkout_config () {
> > +     if test $# -ne 2
> > +     then
> > +             BUG "set_checkout_config() requires two arguments"
> > +     fi &&
>
> A usage comment is typically helpful for these helpers:
>
> # set_checkout_config <workers> <threshold>
> # sets global config values to use the given number of
> # workers when the given threshold is met.

OK, I'll change that.

> > +
> > +     test_config_global checkout.workers $1 &&
> > +     test_config_global checkout.thresholdForParallelism $2
> > +}
> > +
> > +# Run "${@:2}" and check that $1 checkout workers were used
> > +test_checkout_workers () {
>
> This simpler doc style works, too.
>
> > +     if test $# -lt 2
> > +     then
> > +             BUG "too few arguments to test_checkout_workers()"
> > +     fi &&
> > +
> > +     expected_workers=$1 &&
> > +     shift &&
> > +
> > +     rm -f trace &&
> > +     GIT_TRACE2="$(pwd)/trace" "$@" &&
> > +
> > +     workers=$(grep "child_start\[..*\] git checkout--worker" trace | wc -l) &&
> > +     test $workers -eq $expected_workers &&
> > +     rm -f trace
>
> I wonder if this should be a "test_when_finished rm -f trace" being
> recorded earlier in the step.It would also benefit from using a more
> specific name than "trace". Something like "trace-test-checkout-workers"
> would be unlikely to collide with someone else's trace.

Good idea, I'll change the trace file name.

Unfortunately, I think we won't be able to use `test_when_finished`
here as this function is sometimes called inside subshells, and
`test_when_finished` doesn't work in this situation :(

> > +# Verify that both the working tree and the index were created correctly
> > +verify_checkout () {
>
> Add usage of a repo in $1?

Sure!

> > +     git -C "$1" diff-index --quiet HEAD -- &&
> > +     git -C "$1" diff-index --quiet --cached HEAD -- &&
> > +     git -C "$1" status --porcelain >"$1".status &&
> > +     test_must_be_empty "$1".status
> > +}
>
>
> > +TEST_NO_CREATE_REPO=1
> > +. ./test-lib.sh
> > +. "$TEST_DIRECTORY/lib-parallel-checkout.sh"
> > +
> > +# Test parallel-checkout with a branch switch containing file creations,
> > +# deletions, and modification; with different entry types. Switching from B1 to
> > +# B2 will have the following changes:
> > +#
> > +# - a (file):      modified
> > +# - e/x (file):    deleted
> > +# - b (symlink):   deleted
> > +# - b/f (file):    created
> > +# - e (symlink):   created
> > +# - d (submodule): created
> > +#
>
> An interesting set of changes. What about a directory/file conflict?
>
> Something like this might be useful:
>
>  # - f/t (file):   deleted
>  # - f (file):     created
>
> in fact, it could be interesting to have a file conflict with each
> of these types, such as the symlink 'e' and the submodule 'd'.

Sure, I'll add those. (But we already have the symlink case with 'e/x'
(file) and 'e' (symlink), no?)

> While we are at it, what about a symlink/submodule conflict? I know
> it makes the test bigger, but doing everything simultaneously through
> a carefully designed repository helps prevent test case bloat.
>
> > +test_expect_success SYMLINKS 'setup repo for checkout with various types of changes' '
>
> Could we split this setup step into two parts? Once could
> set up everything except the symlinks and would not require
> the SYMLINKS prereq. We could then have another test with
> the SYMLINKS prereq that extends B1 and B2 to have symlinks
> and their conflicts. The remaining tests would work on any
> platform without needing the SYMLINKS prereq.

Good point. I think we might be able to create the symlinks with
`test_ln_s_add` and completely get rid of the SYMLINKS prereq :)

> > +test_expect_success SYMLINKS 'sequential checkout' '
> > +     cp -R various various_sequential &&
> > +     set_checkout_config 1 0 &&
> > +     test_checkout_workers 0 \
> > +             git -C various_sequential checkout --recurse-submodules B2 &&
> > +     verify_checkout various_sequential
> > +'
>
> I see all these tests are very similar. Perhaps group
> them to demonstrate their differences?

Makes sense, I'll do that.

> parallel_test_case () {
>         test_expect_success "$1" "
>                 cp -R various $2 &&
>                 set_checkout_config $3 $4 &&
>                 test_checkout_workers $5 \
>                         git -C $2 checkout --recurse-submodules B2 &&
>                 verify_checkout $2
>         "
> }
>
> parallel_test_case 'sequential checkout' \
>         various_sequential 1 0 0
> parallel_test_case 'parallel checkout' \
>         various_parallel 2 0 2
> parallel_test_case 'fallback to sequential checkout (threshold)' \
>         various_sequential_fallback 2 100 0
>
> > +test_expect_success SYMLINKS 'parallel checkout on clone' '
> > +     git -C various checkout --recurse-submodules B2 &&
> > +     set_checkout_config 2 0 &&
> > +     test_checkout_workers 2 \
> > +             git clone --recurse-submodules various various_parallel_clone &&
> > +     verify_checkout various_parallel_clone
> > +'