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Thanks Clark for this great write-up. However, I think the solution to 
the problem in question is richer commands and better output formatting, 
not discarding information.

On 07/03/14 16:30, Clark Boylan wrote:
> But running tests in parallel introduces some fun problems. Like where
> do you send logging and stdout output. If you send it to the console
> it will be interleaved and essentially useless. The solution to this
> problem (for which I am probably to blame) is to have each test
> collect the logging, stdout, and stderr associated to that test and
> attach it to that tests subunit reporting. This way you get all of the
> output associated with a single test attached to that test and don't
> have crazy interleaving that needs to be demuxed. The capturing of

This is not really a problem unique to parallel test runners. Printing 
to the console is just not a great way to handle stdout/stderr in 
general because it messes up the output of the test runner, and nose 
does exactly the same thing as testr in collecting them - except that 
nose combines messages from the 3 sources and prints the output for 
human consumption, rather than in separate groups surrounded by lots of 
{{{random braces}}}.

> this data is toggleable in the test suite using environment variables
> and is off by default so that when you are not using testr you don't
> get this behavior [0]. However we seem to have neglected log capture
> toggles.

Oh wow, there is actually a way to get the stdout and stderr? Fantastic! 
Why on earth are these disabled?

Please, please, please don't turn off the logging too. That's the only 
tool left for debugging now that stdout goes into a black hole.

> Now onto indirectly answering some of the questions you have. If a
> single unittest is producing thousands of lines of log output that is
> probably a bug. The test scope is too large or the logging is too
> verbose or both. To work around this we probably need to make the
> fakeLogger fixture toggleable with configurable log level. Then you
> could do something like `OS_LOG_LEVEL=error tox` and avoid getting all
> of the debug level logs.

Fewer logs is hardly ever what you want when debugging a unit test.

I think what John is looking for is a report at the end of each test run 
that just lists the tests that failed instead of all the details (like 
`testr failing --list`), or perhaps the complete list of tests with the 
coloured pass/fail like IIRC nose does. Since testr's killer feature is 
to helpfully store all of the results for later, maybe this output is 
all you need in the first instance (along with a message telling the 
user what command to run to see the full output, of course), or at least 
that could be an option.

> For examining test results you can `testr load $SUBUNIT_LOG_FILE` then
> run commands like `testr last`, `testr failing`, `testr slowest`, and
> `testr stats` against that run (if you want details on the last run
> you don't need an explicit load). There are also a bunch of tools that
> come with python-subunit like subunit-filter, subunit2pyunit,
> subunit-stats, and so on that you can use to do additional processing.

It sounds like what John wants to do is pass a filter to something like 
`testr failing` or `testr last` to only report a subset of the results, 
in much the same way as it's possible to pass a filter to `testr` to 
only run a subset of the tests.

BTW, since I'm on the subject, testr would be a lot more 
confidence-inspiring if running `testr failing` immediately after 
running `testr` reported the same number of failures, or indeed if 
running `testr` twice in a row was guaranteed to report the same number 
of failures (assuming that the tests themselves are deterministic). I 
can't imagine why one of the subunit processes reporting a test failure 
is considered a failure in itself (that's what it's supposed to do!), 
particularly when `testr failing` manages to filter them out OK.

(I understand that some of the things mentioned above may already have 
been improved since the latest 0.0.18 release. I can't actually find the 
repo at the moment to check, because it's not linked from PyPI or 
Launchpad and 'testrepository' turns out to be an extremely common name 
for things on the Internet.)

cheers,
Zane.