Switching from nose to py.test at Mozilla

Matthieu Agopian slides - http://mathieu.agopian.info/presentations/2015_06_djangocon_europe/

glossary

• test - bit of code to assert other code working
• test runner - gather tests, run them, report
• test suite, build - full collection
• fixture - data fixture (django) OR dependency injection (pytest)

What is pytest

• Holger Krekel
• no boiler place tests (eg assert 1 + 1 == 2) and still get meaningful report
• plugins
• 10 slowest tests –duration=10
• modify tracebacks
• drop to pdb on fail –pdb
• output capture on by default - only display for fails
• mark tests @pytest.mark.functional - run separately
• awesome failure reports - eg comparing dictionaries

dependency injection

• instead of setUp/tearDown ...
• eg. rf, settings provided by pytest-django (request factory, django settings)

parameterisation

• have same test run multiple times with different inputs and expected outputs

config

• pytest.ini - markers to use, default args, test files
• conftest.py - locally for current folder and children - eg use another settings file

plugins

• pytest-django
  • –create-db, –reuse-db, to save time
  • @pytest.mark.django_db - explicit, see tests that will be slow. Can be set in conftest.py
• pytest-cov
• pytest-cache (–lf - only run last failed test)
• pytest-xdist

why change?

• is better maintained
• compatible with current tests
• will be better for future tests

why not?

• no dependency injection for nose classes
• can still use the autouse fixtures
• no data fixture bundling

can convert some asserts quickly