Re: [Tarantool-patches] [PATCH] test: use grep_log in tests

[Alexander Turenko <alexander.turenko@tarantool.org>]

I like the simplification of the test you made. Please, consider several
comments below.

Please, see test-run patch comments first (see [1]), because I proposed
to rename the option from `path` to `filename`.

[1]: https://lists.tarantool.org/pipermail/tarantool-patches/2020-March/014638.html

WBR, Alexander Turenko.

> test: use grep_log in tests

Nit: I would make the commit header a bit more certain and point the
test name right here.

>
> Refactoring: replace grep_for_broken_lsn with grep_log from test_run.
> ---
>  test/xlog/panic_on_broken_lsn.result   | 50 +++++++++-----------------
>  test/xlog/panic_on_broken_lsn.test.lua | 29 ++++-----------
>  2 files changed, 22 insertions(+), 57 deletions(-)

>  -- Check that log contains the mention of broken LSN and the request printout
> -grep_broken_lsn(fio.pathjoin(fio.cwd(), 'panic.log'), 1)
> +path = fio.pathjoin(fio.cwd(), 'panic.log')
> +---
> +...
> +str = "LSN for 1 is used twice or COMMIT order is broken: confirmed: 1, new: 1"
>  ---
> -- '{type: ''REPLACE'', replica_id: 1, space_id: 272, index_id: 0, tuple: ["t0", "v1"]}'
> +...

I would keep the request information as proof that we found the log
entry generated by the errinj above and not something else. May be
implemented like so:

 | path = fio.pathjoin(fio.cwd(), 'replica.log')
 | str = string.format("LSN for 1 is used twice or COMMIT order is broken: confirmed: %d, new: %d, req: .*", lsn, lsn)
 | found = test_run:grep_log(nil, str, 256, {path = path})
 | (found:gsub('^.*, req: ', ''):gsub('lsn: %d+', 'lsn: <lsn>'))

(See below re 256.)

(Parenthesis are to discard the second return value of string.gsub().)

>  -- Check that log contains the mention of broken LSN and the request printout
> -grep_broken_lsn(fio.pathjoin(fio.cwd(), 'panic.log'), 1)
> -
> +path = fio.pathjoin(fio.cwd(), 'panic.log')
> +str = "LSN for 1 is used twice or COMMIT order is broken: confirmed: 1, new: 1"
> +test_run:grep_log(nil, str, nil, {path = path})~= nil

Nit: spaces are needed around '~='.

I would keep 265 bytes window (there is `bytes` option in grep_log()).
Lesser value is more safe: if the expected log entry is not appear we
can occasionally found the entry from another test if the window is big
enough for this. It means that the test may pass even when is should
not. So it is good to keep the window small.