Document way to customize abbreviation (elipsis) on AssertionError

[ssbarnea]

I keep getting errors that I cannot debug because the printed AssertionError is censored so much that makes impossible to see what was the difference.

Adding -vvvv did not help at all changing the way exceptions are rendered.

      assert l in out

E AssertionError: assert 'instance docker ansible default false false' in 'Instance Name Driver Name Provisioner Name Scenario Name Created Converged\n--------------- ---------...i-node false false\ninstance-2 docker ansible multi-node false false\n'

I did try to research the subject a lot online but I was not able to find any solution that would allow me to disable or customize when abbreviation happens, to make the limit upwards.

I raised this to PyTest because I am looking for a solution that can enable this at the entire test-suite and not on a specific file with tests, being able to do it globally is key for big projects.

Some resources I found:

• https://stackoverflow.com/questions/50608443/how-do-i-get-pycharm-to-show-entire-error-diffs-from-pytest -- I was not able to find a way to hack DEFAULT_MAX_CHARS
• https://stackoverflow.com/questions/38000993/how-can-i-get-my-assertions-in-pytest-to-stop-being-abbreviated-with-ellipsis

[blueyed]

Try env CI=true …, but it does not help here.
(It is an annoying thing, I know - there are some issues/ideas in that regard open already)
Related: blueyed#63
The problem here is that the internal pytest_assertrepr_compare hook does nothing here (for `op = "in"), and the assertion rewrite having it truncated already anyway.
Somehow related docs: https://github.com/blueyed/pytest/blob/49f6aaf725610acf67087b0a38dc69e636c7402f/doc/en/assert.rst#defining-your-own-explanation-for-failed-assertions

[ssbarnea]

One year later and I am facing again the same issue, a bug caused by an incomplete feature, one that cannot be disabled, the truncation.

Can we please do something about it? For some projects this is testing PITA as the comparisons are almost always bigger than the limit and the user is left clueless to face the what is behind those ellipses? questions.

[nicoddemus]

Indeed this is frustrating, thanks @ssbarnea for bringing it to light again.

I've opened #8391 as an attempt to fix this, feedback welcome.

[ssbarnea]

I think it was #8391 -- going to test it now.

[nicoddemus]

Oops yes, fixed my comment.