From: Junio C Hamano <gitster@pobox.com>
To: Derrick Stolee <stolee@gmail.com>
Cc: "Ævar Arnfjörð Bjarmason" <avarab@gmail.com>,
git@vger.kernel.org, "David Turner" <novalis@novalis.org>,
"Elijah Newren" <newren@gmail.com>,
"Matheus Tavares" <matheus.bernardino@usp.br>,
"Jeff King" <peff@peff.net>,
"Derrick Stolee" <derrickstolee@github.com>,
"Đoàn Trần Công Danh" <congdanhqx@gmail.com>
Subject: Re: test-lib.sh musings: test_expect_failure considered harmful
Date: Wed, 13 Oct 2021 10:16:18 -0700 [thread overview]
Message-ID: <xmqq4k9kj15p.fsf@gitster.g> (raw)
In-Reply-To: <d643863c-7683-fe4b-e4f2-3fefc475006b@gmail.com> (Derrick Stolee's message of "Wed, 13 Oct 2021 09:05:08 -0400")
Derrick Stolee <stolee@gmail.com> writes:
>> But even with the shortcomings of expect_failure, it still is much
>> better than claiming that we expect a bogus outcome.
>>
>> Improving the shortcomings of expect_failure would be a much better
>> use of our time than advocating an abuse of expect_sucess, I would
>> think.
>
> I agree that test_expect_failure has these drawbacks. I've recently
> been using _expect_success to document "bad" behavior so we can verify
> that behavior changes when that behavior is fixed. But it does have
> the drawback of looking like we claim the result is by design.
Yeah, I think I saw (and I think I used the same technique myself)
people expect a bad output with test_expect_success with an in-code
(not in-log) comment that explicitly says "This documents the
current behaviour, which is wrong", and that is a very acceptable
solution, I would think.
> One possible way to correct this is to create a "test_expected_failure"
> helper that could be placed on the step(s) of the &&-chain that are
> expected to fail. The helper could set some variable to true if the
> failure is hit, and false otherwise. It can also convert a failure
> into a positive result. Then, test_expect_failure could look for that
> variable's value (after verifying that the &&-chain returns success)
> to show that all expected failures completed correctly.
Yup, I would very much like the direction, and further imagine that
the above approach can be extended to ...
> This could have the side-effect of having a "fixed" test_expect_failure
> show as a failed test, not a "TODO" message.
... avoid such downside. Perhaps call that magic "we know this step
fails currently" test_known_breakage and declare that we deprecate
the use of test_expect_failure in new tests. Such a test might look
like this:
test_expect_success 'commit error message should not duplicate' '
test_when_finished "chmod -R u+rwx ." &&
chmod u-rwx .git/objects/ &&
orig_head=$(git rev-parse HEAD) &&
test_must_fail git commit --allow-empty -m "read-only" 2>rawerr &&
grep "insufficient permission" rawerr >err &&
test_known_breakage test_line_count = 1 err &&
new_head=$(git rev-parse HEAD) &&
test "$orig_head" = "$new_head"
'
which may use your trick to turn both failure and success to OK (to
let the remainder of the test to continue) but signal the
surrounding test_expect_success to say either "TODO know breakage"
or "Fixed".
Thanks.
next prev parent reply other threads:[~2021-10-13 17:16 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-12 9:23 test-lib.sh musings: test_expect_failure considered harmful Ævar Arnfjörð Bjarmason
2021-10-12 16:45 ` Junio C Hamano
2021-10-13 10:10 ` Ævar Arnfjörð Bjarmason
2021-10-13 13:05 ` Derrick Stolee
2021-10-13 17:16 ` Junio C Hamano [this message]
2021-10-14 17:11 ` Ævar Arnfjörð Bjarmason
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