Exit pytest if a collection error occours

[fontealpina]

If a collection error occurs, is there a way to terminate immediately pytest execution after collection, avoiding the execution of all the tests (even the ones properly collected)?
Basically I need to start test execution only if there are no import errors.
So for instance, now if there is a collection error I get:

$ pytest test/test_01/test_01.py test/test_02/test_02.py test/test_03/test_03.py -v -s
============================ test session starts =============================
platform linux2 -- Python 2.6.6 -- py-1.4.26 -- pytest-2.7.0.dev1 -- /usr/bin/python
collected 2 items / 1 errors

test/test_01/test_01.py::TestBug::test_n_01 PASSED
test/test_02/test_02.py::TestBug::test_n_02 PASSED

=================================== ERRORS ===================================
________________ ERROR collecting test/test_03/test_03.py _________________
import file mismatch:
a description of the import error
================ 2 passed, 1 error in 0.17 seconds ================

I would get something like this instead:

$ pytest test/test_01/test_01.py test/test_02/test_02.py test/test_03/test_03.py -v -s
============================ test session starts =============================
platform linux2 -- Python 2.6.6 -- py-1.4.26 -- pytest-2.7.0.dev1 -- /usr/bin/python
collected 2 items / 1 errors
=================================== ERRORS =============================
________________ ERROR collecting test/test_03/test_03.py _______________________
import file mismatch:
a description of the import error
================================ 1 error in 0.17 seconds ======================

Is there an options that allows that?
Or maybe this can be done with a plugin?
Thanks

[The-Compiler]

You can easily do this with a local plugin, e.g. by putting this in a conftest.py:

import pytest

def pytest_collectreport(report):
    if report.failed:
        raise pytest.UsageError("Errors during collection, aborting")

Then even if tests are collected, your hook will exit before they are run:

collecting 1 items / 1 errors
================================================ ERRORS =================================================
_____________________________________ ERROR collecting test_two.py ______________________________________
test_two.py:1: in <module>
    import asifjsafpo
E   ImportError: No module named 'asifjsafpo'
======================================== 1 error in 0.01 seconds ========================================
ERROR: Errors during collection, aborting

[fontealpina]

Great, it works as I was expecting!
Thanks

[nicoddemus]

@fontealpina would you consider writing a short blog post with this trick in pytest-tricks? 😉

cc @hackebrot

[fontealpina]

@nicoddemus it is a pleasure for me. I'll do it as soon as possible.

[nicoddemus]

Nice, thanks! 😎

[hpk42]

Actually i think it's worthwhile to consider if we want to consider changing the default to stop if a collection error occurs. Having good defaults is a major goal IMHO. Who ever likes to execute tests when there are collection errors? Whenever i see them i usually want to first see what's going wrong with collection before considering anything else. If there is a real need we can introduce a --continue-on-collection-errors option or so.

[The-Compiler]

Hmm, I actually agree with that - let's reopen this

[nicoddemus]

I agree... if I see collection errors the first thing I do is to immediately hit CTRL+C to stop the run. 😁