Fix ZeroDivisionError with 0 collected tests

[blueyed]

This can easily happen with pytest-testmon.

Here's a quick checklist that should be present in PRs:

• Add a new news fragment into the changelog folder
  • name it $issue_id.$type for example (588.bug)
  • if you don't have an issue_id change it to the pr id after creating the pr
  • ensure type is one of removal, feature, bugfix, vendor, doc or trivial
  • Make sure to use full sentences with correct case and punctuation, for example: "Fix issue with non-ascii contents in doctest text files."
• Target: for bugfix, vendor, doc or trivial fixes, target master; for removals or features target features;
• Make sure to include reasonable tests for your change if necessary

[nicoddemus]

@blueyed thanks for the PR! 👍

Can you add a CHANGELOG entry and a test case to avoid a future regression? I tried adding one myself:

    def test_zero_tests_collected(self, testdir):
        output = testdir.runpytest()
        output.stdout.re_match_lines([
            r'=* 0 tests collected =*',
        ])

But this does not fail with a ZeroDivisionError...

[coveralls]

Coverage decreased (-0.009%) to 92.679% when pulling 0f5fb7e on blueyed:fix-ZeroDivisionError into 4d2f05e on pytest-dev:master.

[blueyed]

Might take a while before coming back to it.

Here is the stacktrace for reference:

==================================================================================== test session starts =====================================================================================
platform linux -- Python 3.6.3, pytest-3.3.0, py-1.5.2, pluggy-0.6.0
testmon=True, changed files: covimerage/logger.py,tests/test_logging.py, skipping collection of 56 items, run variant: default
rootdir: …/src/covimerage, inifile: setup.cfg
plugins: testmon-0.9.6, pdb-0.2.0, mock-1.6.3, cov-2.5.1, annotate-1.0.1
collected 59 items                                                                                                                                                                           

tests/test_cli.py FFFFFFFFFFFF
INTERNALERROR> Traceback (most recent call last):
INTERNALERROR>   File "…/src/covimerage/.venv/lib/python3.6/site-packages/_pytest/main.py", line 103, in wrap_session
INTERNALERROR>     session.exitstatus = doit(config, session) or 0
INTERNALERROR>   File "…/src/covimerage/.venv/lib/python3.6/site-packages/_pytest/main.py", line 140, in _main
INTERNALERROR>     config.hook.pytest_collection(session=session)
INTERNALERROR>   File "…/src/covimerage/.venv/lib/python3.6/site-packages/pluggy/__init__.py", line 617, in __call__
INTERNALERROR>     return self._hookexec(self, self._nonwrappers + self._wrappers, kwargs)
INTERNALERROR>   File "…/src/covimerage/.venv/lib/python3.6/site-packages/pluggy/__init__.py", line 222, in _hookexec
INTERNALERROR>     return self._inner_hookexec(hook, methods, kwargs)
INTERNALERROR>   File "…/src/covimerage/.venv/lib/python3.6/site-packages/pluggy/__init__.py", line 216, in <lambda>
INTERNALERROR>     firstresult=hook.spec_opts.get('firstresult'),
INTERNALERROR>   File "…/src/covimerage/.venv/lib/python3.6/site-packages/pluggy/callers.py", line 201, in _multicall
INTERNALERROR>     return outcome.get_result()
INTERNALERROR>   File "…/src/covimerage/.venv/lib/python3.6/site-packages/pluggy/callers.py", line 76, in get_result
INTERNALERROR>     raise ex[1].with_traceback(ex[2])
INTERNALERROR>   File "…/src/covimerage/.venv/lib/python3.6/site-packages/pluggy/callers.py", line 180, in _multicall
INTERNALERROR>     res = hook_impl.function(*args)
INTERNALERROR>   File "…/src/covimerage/.venv/lib/python3.6/site-packages/_pytest/main.py", line 150, in pytest_collection
INTERNALERROR>     return session.perform_collect()
INTERNALERROR>   File "…/src/covimerage/.venv/lib/python3.6/site-packages/_pytest/main.py", line 643, in perform_collect
INTERNALERROR>     config=self.config, items=items)
INTERNALERROR>   File "…/src/covimerage/.venv/lib/python3.6/site-packages/pluggy/__init__.py", line 617, in __call__
INTERNALERROR>     return self._hookexec(self, self._nonwrappers + self._wrappers, kwargs)
INTERNALERROR>   File "…/src/covimerage/.venv/lib/python3.6/site-packages/pluggy/__init__.py", line 222, in _hookexec
INTERNALERROR>     return self._inner_hookexec(hook, methods, kwargs)
INTERNALERROR>   File "…/src/covimerage/.venv/lib/python3.6/site-packages/pluggy/__init__.py", line 216, in <lambda>
INTERNALERROR>     firstresult=hook.spec_opts.get('firstresult'),
INTERNALERROR>   File "…/src/covimerage/.venv/lib/python3.6/site-packages/pluggy/callers.py", line 201, in _multicall
INTERNALERROR>     return outcome.get_result()
INTERNALERROR>   File "…/src/covimerage/.venv/lib/python3.6/site-packages/pluggy/callers.py", line 76, in get_result
INTERNALERROR>     raise ex[1].with_traceback(ex[2])
INTERNALERROR>   File "…/src/covimerage/.venv/lib/python3.6/site-packages/pluggy/callers.py", line 180, in _multicall
INTERNALERROR>     res = hook_impl.function(*args)
INTERNALERROR>   File "…/src/covimerage/.venv/lib/python3.6/site-packages/testmon/pytest_testmon.py", line 180, in pytest_collection_modifyitems
INTERNALERROR>     self.report_if_failed(item.nodeid)
INTERNALERROR>   File "…/src/covimerage/.venv/lib/python3.6/site-packages/testmon/pytest_testmon.py", line 166, in report_if_failed
INTERNALERROR>     self.config.hook.pytest_runtest_logreport(report=test_report)
INTERNALERROR>   File "…/src/covimerage/.venv/lib/python3.6/site-packages/pluggy/__init__.py", line 617, in __call__
INTERNALERROR>     return self._hookexec(self, self._nonwrappers + self._wrappers, kwargs)
INTERNALERROR>   File "…/src/covimerage/.venv/lib/python3.6/site-packages/pluggy/__init__.py", line 222, in _hookexec
INTERNALERROR>     return self._inner_hookexec(hook, methods, kwargs)
INTERNALERROR>   File "…/src/covimerage/.venv/lib/python3.6/site-packages/pluggy/__init__.py", line 216, in <lambda>
INTERNALERROR>     firstresult=hook.spec_opts.get('firstresult'),
INTERNALERROR>   File "…/src/covimerage/.venv/lib/python3.6/site-packages/pluggy/callers.py", line 201, in _multicall
INTERNALERROR>     return outcome.get_result()
INTERNALERROR>   File "…/src/covimerage/.venv/lib/python3.6/site-packages/pluggy/callers.py", line 76, in get_result
INTERNALERROR>     raise ex[1].with_traceback(ex[2])
INTERNALERROR>   File "…/src/covimerage/.venv/lib/python3.6/site-packages/pluggy/callers.py", line 180, in _multicall
INTERNALERROR>     res = hook_impl.function(*args)
INTERNALERROR>   File "…/src/covimerage/.venv/lib/python3.6/site-packages/_pytest/terminal.py", line 272, in pytest_runtest_logreport
INTERNALERROR>     self.write_fspath_result(rep.nodeid, letter)
INTERNALERROR>   File "…/src/covimerage/.venv/lib/python3.6/site-packages/_pytest/terminal.py", line 164, in write_fspath_result
INTERNALERROR>     self._write_progress_information_filling_space()
INTERNALERROR>   File "…/src/covimerage/.venv/lib/python3.6/site-packages/_pytest/terminal.py", line 322, in _write_progress_information_filling_space
INTERNALERROR>     msg = self._get_progress_information_message()
INTERNALERROR>   File "…/src/covimerage/.venv/lib/python3.6/site-packages/_pytest/terminal.py", line 316, in _get_progress_information_message
INTERNALERROR>     progress = self._progress_items_reported * 100 // self._session.testscollected
INTERNALERROR> ZeroDivisionError: integer division or modulo by zero

===================================================================================== 4 tests deselected =====================================================================================
========================================================================== 13 failed, 4 deselected in 0.06 seconds ===========================================================================

[nicoddemus]

@blueyed thanks that helps.

I can see that testmon is triggering a self.config.hook.pytest_runtest_logreport(report=test_report) during pytest_collect_modifyitems, which explains why session.testscollected might be zero at that point.

[nicoddemus]

Managed to write a test which reproduces the issue, thanks @blueyed!

[coveralls]

Coverage increased (+0.002%) to 92.69% when pulling 6bbd741 on blueyed:fix-ZeroDivisionError into 4d2f05e on pytest-dev:master.

[blueyed]

Awesome, thanks!