Refactor class StepwisePlugin.

[henrykironde]

Initialize class properties
Check attributes before accessing them, LBYL

checklist

• Create a new changelog file in the changelog folder, with a name like <ISSUE NUMBER>.<TYPE>.rst. See changelog/README.rst for details.
• Target the master branch for bug fixes, documentation updates and trivial changes.
• Target the features branch for new features and removals/deprecations.
• Include documentation when adding new features.
• Include new tests or update existing tests when applicable.
• Add yourself to AUTHORS in alphabetical order;

ref: #4333

[blueyed]

Have not really checked, but see #4304 (changelog file should be improved/renamed).

Does this fix it completely? A test would be good to have!

[blueyed]

3.10.1 is not there yet.. ;)
Also this should be more specific about the fix.

[codecov]

Codecov Report

Merging #4335 into master will decrease coverage by <.01%.
The diff coverage is 80%.

@@            Coverage Diff             @@
##           master    #4335      +/-   ##
==========================================
- Coverage   95.84%   95.84%   -0.01%     
==========================================
  Files         111      111              
  Lines       24880    24884       +4     
  Branches     2430     2432       +2     
==========================================
+ Hits        23847    23849       +2     
  Misses        736      736              
- Partials      297      299       +2

Flag	Coverage Δ
#docs	28.92% <30%> (ø)	⬆️
#doctesting	28.92% <30%> (ø)	⬆️
#linting	28.92% <30%> (ø)	⬆️
#linux	95.62% <80%> (-0.01%)	⬇️
#nobyte	91.83% <80%> (-0.01%)	⬇️
#numpy	93.01% <80%> (-0.01%)	⬇️
#pexpect	41.68% <30%> (ø)	⬆️
#py27	94.01% <80%> (-0.01%)	⬇️
#py34	92.14% <80%> (+0.05%)	⬆️
#py35	92.15% <80%> (+0.05%)	⬆️
#py36	93.9% <80%> (ø)	⬆️
#py37	92.19% <80%> (+0.05%)	⬆️
#trial	93.01% <80%> (-0.01%)	⬇️
#windows	93.95% <80%> (-0.01%)	⬇️
#xdist	93.72% <80%> (ø)	⬆️

Impacted Files	Coverage Δ
src/_pytest/stepwise.py	92.85% <80%> (-3.3%)	⬇️

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[henrykironde]

@blueyed, this seems to fix the issue. I would love to make a test case but I don't seem to get the organization of the tests.
However the logic to create testing for the pytest_sessionfinish function would be:

• Start a session.

• Initialize StepwisePlugin class object and add the session.

If the test are to pass, testing that is covered
The main goal is to have the tests fail, and parse a "--stepwise".

• If active self.active = config.getvalue("stepwise") is set,
  we should have some values in self.lastfailed
  from self.config.cache.set("cache/stepwise", self.lastfailed)
  else expected values will be []
  from self.config.cache.set("cache/stepwise", [])

[nicoddemus]

Thanks @henrykironde for the contribution.

As @blueyed mentioned before, this is a duplicate of #4304.

In pytest many contributed tests use the testdir fixture to create small test cases which demonstrate an issue, run pytest, and check the output. There are tons of examples in testing, browse around and I'm sure you will get the gist of it.

Closing this now as this issue in particular was already fixed by #4304, but we look forward for your future contributions. 👍