Make manage.py test display the test tags that are in use

[Rich Jones]

_This ticket is part of the Django Test Output Beautification initiative: https://code.djangoproject.com/ticket/29101_

Django 1.10 introduced a wonderful new feature, test tagging, which allows the user running tests to control which tests are included and excluded in a test execution. This is particularly handy in complicated and conditional continuous integration setups, which may require lots of different tag inclusions and exclusions.

The annoying part is that the default test output, and even the test output with higher verbosity levels, never displays which tests are excluded or included.

I'd be great if this information could be displayed in three ways during a test execution: Once during initialization, to show which tags were included or excluded, once for each test as it is skipped, and once during the final tally.

So, at the beginning:

System check identified no issues (0 silenced).
Running tests, excluding [slow, veryslow].

For each test skipped:

========================
Testing 'test_good_file_grouping'
(data_refinery_workers.downloaders.test_transcriptome_index.DownloadTranscriptomeIndexTestCase)
_Makes sure that proper file group runs the pipeline._
-----------------------------------------------------
...
Ok!

========================
Skipping 'test_good_file_grouping'
(data_refinery_workers.downloaders.test_transcriptome_index.DownloadTranscriptomeIndexTestCase)
[veryslow]
-----------------------------------------------------

And finally, at the end:

----------------------------------------------------------------------
Ran 38 tests in 34.808s. Skipped 4 tests.

This should work appropriately for all of the different tag-related test arguments.

It'd also be nice if this test output was appropriately colorized.

Related tickets:
https://code.djangoproject.com/ticket/29105
https://code.djangoproject.com/ticket/22449
https://code.djangoproject.com/ticket/29105

[Tim Graham]

The tests are filtered by their tag before the test suite starts running, therefore displaying the skipped tests isn't feasible. Even if it were feasible, I wouldn't want that in my own use of test tagging. When running Django's test suite with --selenium, for example, there are about 40 tests that run out of hundreds in the complete test suite. Showing all the skipped tests would just clutter the output for this use case.

Making DiscoverRunner displaying the tags seems fine (at verbosity 2 or greater).

[Sanyam Khurana]

Hey, I'm starting to work on this issue. Will submit a PR soon.

[Sanyam Khurana]

I've added a patch. Wasn't able to write test fully. Need a pointer on how to proceed. I've mentioned the issue in the PR: ​https://github.com/django/django/pull/9658

[Tim Graham]

I think you'll use django.test.utils.captured_stdout for the test.

[Sanyam Khurana]

Oh, yes. I don't know why I was confused about that.

That did the trick. Thank you so much. I've updated the Pull Request.

[Tim Graham <timograham@…>]

In 5a669ae2:

Fixed #29106 -- Made DiscoverRunner display selected test tags.