#306 Some Fun pytesting Tools

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Brian #1: Awesome pytest speedup

• Neyts Zupan
• A checklist of best practices to speed up your pytest suite.
• as a talk at Plone NAMUR 2022
• Measure first
• Then make sure (all items have explanations)
  • Hardware is fast
    • use a faster computer
    • also try a self-hosted runner
      • seriously, a dedicated computer (or a few) for making test runs faster might be worth it. CI resources are usually slower in cloud than local, and even expensive VM farms are often slower. Try local
  • Collection is fast
    • utilize norecursedirs and specifying the location of the tests, either on the command line or with testpaths
  • PYTHONDONTWRITEBYTECODE=1 is set
    • might help
  • Built-in pytest plugins are disabled
    • try -p no:pastebin -p no:nose -p no:doctest
  • Only a subset of tests are executed
    • Especially when developing or debugging, run a subset and skip the slow tests.
  • Network access is disabled
    • pytest-socket can make sure of that
  • Disk access is disabled
    • interesting idea
  • Database access is optimized
    • great discussion here, including using truncate and rollback.
  • Tests run in parallel
    • pytest-xdist or similar
• Then keep them fast
  • monitor test speed

Michael #2: Strive to travel without a laptop

• Prompt from Panic for SSH on iThings
• github.dev for an editor on iPad
• Push to branch for continuous deployment
• BTW, Apple could just make M1 iPads boot to macOS rather than chase silly multi windowing systems (stage manager, etc, etc)

Brian #3: Some fun tools from the previous testing article

• hyperfine for timing the whole suite
• pytest --``durations 10 for finding test times of slowest 10 tests
  • leave the 10 off to find times of everything, sorted
• pyinstrument for profiling with nice tree structures
  • and how to use it with pytest
• pytest-socket disables network calls with --disable-socket, helping to find tests that use network calls.
• pyfakefs, a fake file system that mocks the Python file system modules. “Using pyfakefs, your tests operate on a fake file system in memory without touching the real disk.”
• BlueRacer.io

Michael #4: Refurb

• A tool for refurbishing and modernizing Python codebases
• Think of it as suggesting the pythonic line of code.
• A little sampling of what I got on Talk Python Training
  • file.py:186:25 [FURB106]: Replace x.replace("\t", " ") with x.expandtabs(1)
  • file.py:128:17 [FURB131]: Replace del x[y] with x.pop(y)
  • file.py:103:17 [FURB131]: Replace del x[y] with x.pop(y)
  • file.py:112:39 [FURB109]: Replace not in [x, y, z] with not in (x, y, z)
  • file.py:45:5 [FURB131]: Replace del x[y] with x.pop(y)
  • file.py:81:21 [FURB131]: Replace del x[y] with x.pop(y)
  • file.py:143:9 [FURB131]: Replace del x[y] with x.pop(y)
  • file.py:8:50 [FURB123]: Replace list(x) with x.copy()
• You don’t always want the change, can suppress the recommendation with either a CLI flag or comment.

Extras

Michael:

• Back on episode 54 in 2017 we discussed python apps in systemd daemons.
  • Multiprocessing allows for a cool way to save on server memory
  • Do the scheduled work a multiprocessing.Process
  • Here’s an example from Talk Python Training
• Completely rewrote search UI for Talk Python courses
• Google analytics is now illegal?
• Fleet is finally in public preview
• I’ll be on a JetBrains/PyCharm webcast Thursday.

Joke: Tests pass