Test & Code

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130: virtualenv activation prompt consistency across shells - an open source dev and test adventure - Brian Skinn Sep 13, 2020

Show notes

virtualenv supports six shells: bash, csh, fish, xonsh, cmd, posh. Each handles prompts slightly differently. Although the virtualenv custom prompt behavior should be the same across shells, Brian Skinn noticed inconsistencies. He set out to fix those inconsistencies. That was the start of an adventure in open source collaboration, shell prompt internals, difficult test problems, and continuous integration quirks.

Brian Skinn initially noticed that on Windows cmd, a space was added between a prefix defined by --prompt and the rest of the prompt, whereas on bash no space was added.

For reference, there were/are three nominal virtualenv prompt modification behaviors, all of which apply to the prompt changes that are made at the time of virtualenv activation:

If the environment variable VIRTUAL_ENV_DISABLE_PROMPT is defined and non-empty at activation time, do not modify the prompt at all. Otherwise:
If the --prompt argument was supplied at creation time, use that argument as the prefix to apply to the prompt; or,
If the --prompt argument was not supplied at creation time, use the default prefix of "() " as the prefix (the environment folder name surrounded by parentheses, and with a trailing space after the last paren.

Special Guest: Brian Skinn.

Links:

129: How to Test Anything - David Lord Sep 07, 2020

Show notes

I asked people on twitter to fill in "How do I test _____?" to find out what people want to know how to test.
Lots of responses. David Lord agreed to answer them with me.
In the process, we come up with lots of great general advice on how to test just about anything.

Specific Questions people asked:

What makes a good test?
How do you test web app performance?
How do you test cookie cutter templates?
How do I test my test framework?
How do I test permission management?
How do I test SQLAlchemy models and pydantic schemas in a FastAPI app?
How do I test warehouse ETL code?
How do I test and mock GPIO pins on hardware for code running MicroPython on a device?
How do I test PyQt apps?
How do I test web scrapers?
Is it the best practice to put static html in your test directory or just snippets stored in string variables?
What's the best way to to test server client API contracts?
How do I test a monitoring tool?

We also talk about:

What is the Flask testing philosophy?
What do Flask tests look like?
Flask and Pallets using pytest
Code coverage

Some of the resulting testing strategies:

Set up some preconditions. Run the function. Get the result.
Don't test external services.
Do test external service failures.
Don't test the frameworks you are using.
Do test your use of a framework.
Use open source projects to learn how something similar to your project tests things.
Focus on your code.
Focus on testing your new code.
Try to architect your application such that actual GUI testing is minimal.
Split up a large problem into smaller parts that are easier to test.
Nail down as many parts as you can.

Special Guest: David Lord.

128: pytest-randomly - Adam Johnson Aug 28, 2020

Show notes

Software tests should be order independent. That means you should be able to run them in any order or run them in isolation and get the same result.

However, system state often gets in the way and order dependence can creep into a test suite.
One way to fight against order dependence is to randomize test order, and with pytest, we recommend the plugin pytest-randomly to do that for you.

The developer that started pytest-randomly and continues to support it is Adam Johnson, who joins us today to discuss pytest-randomly and another plugin he also wrote, called pytest-reverse.

Special Guest: Adam Johnson.

Links:

127: WFH, WTF? - Tips and Tricks for Working From Home - Reuven Lerner & Julian Sequeira Aug 24, 2020

Show notes

Many people have been working from home now that are not used to working from home.
Or at least are working from home more than they ever did before. That's definitely true for me.
Even though I've been working from home since March, I wanted some tips from people who have been doing it longer.

Julian Sequeira, of PyBites fame, has been working from home for about a year.
Reuven Lerner, an amazing Python trainer, has been working from home for much longer.

We originally had a big list of WFH topics. But we had so much fun with the tips and tricks part, that that's pretty much the whole episode.

But there's lots of great tips and tricks, so I'm glad we focused on that.

Special Guests: Julian Sequeira and Reuven Lerner.

Links:

PyBites — Julian's site for teaching Python
Teaching Python and data science around the world — Reuven Lerner
Bonbon - Wikipedia
Test & Code Mailing List — Join for your chance to win a free course from Talk Python Training. One course given away every week for 6 weeks.

126: Data Science and Software Engineering Practices ( and Fizz Buzz ) - Joel Grus Aug 16, 2020

Show notes

Researches and others using data science and software need to follow solid software engineering practices. This is a message that Joel Grus has been promoting for some time.

Joel joins the show this week to talk about data science, software engineering, and even Fizz Buzz.

Topics include:

Software Engineering practices and data science
Difficulties with Jupyter notebooks
Code reviews on experiment code
Unit tests on experiment code
Finding bugs before doing experiments
Tests for data pipelines
Tests for deep learning models
Showing researchers the value of tests by showing the bugs found that wouldn't have been found without them.
"Data Science from Scratch" book
- Showing testing during teaching Data Science
"Ten Essays on Fizz Buzz" book
- Meditations on Python, mathematics, science, engineerign and design
- Testing Fizz Buzz
- Different algorithms and solutions to an age old interview question.
If not Fizz Buzz, what makes a decent coding interview question.
pytest
hypothesis
Math requirements for data science

Special Guest: Joel Grus.

Links:

125: pytest 6 - Anthony Sottile Aug 07, 2020

Show notes

pytest 6 is out. Specifically, 6.0.1, as of July 31.

And there's lots to be excited about.
Anthony Sottile joins the show to discuss features, improvements, documentation updates and more.

Full release notes / changelog

Some of what we talk about:

How to update (at least, how I do it)
- Run your test suites with 5.4.3 or whatever the last version you were using
- Update to 6
- Run again. Same output? Probably good.
- If there are any warnings, maybe fix those.
- You can also run with pytest -W error to turn warnings into errors.
- Then find out all the cool stuff you can do now
New Features
- pytest now supports pyproject.toml files for configuration.
  - but remember, toml syntax is different than ini files. mostly quotes are needed
- pytest now includes inline type annotations and exposes them to user programs.
  - Most of the user-facing API is covered, as well as internal code.
- New command-line flags --no-header and --no-summary
- A warning is now shown when an unknown key is read from a config INI file.
  - The --strict-config flag has been added to treat these warnings as errors.
- New required_plugins configuration option allows the user to specify a list of plugins, including version information, that are required for pytest to run. An error is raised if any required plugins are not found when running pytest.
Improvements
- You can now pass output to things like less and head that close the pipe passed to them.
  - thank you!!!
- Improved precision of test durations measurement.
  - use --durations=10 -vv to capture and show durations
- Rich comparison for dataclasses and attrs-classes is now recursive.
- pytest --version now displays just the pytest version,
  - while pytest --version --version displays more verbose information including plugins.
- --junitxml now includes the exception cause in the message XML attribute for failures during setup and teardown.
Improved Documentation
- Add a note about --strict and --strict-markers and the preference for the latter one.
- Explain indirect parametrization and markers for fixtures.
Bug Fixes
Deprecations
Trivial/Internal Changes
Breaking Changes you might need to care about before upgrading
- PytestDeprecationWarning are now errors by default.
  - Check the deprecations and removals page if you are curious.
- -k and -m internals were rewritten to stop using eval(), this results in a few slight changes but overall makes them much more consistent
- testdir.run().parseoutcomes() now always returns the parsed nouns in plural form.
  - I'd say that's an improvement

Special Guest: Anthony Sottile.

Links:

124: pip dependency resolver changes Aug 03, 2020

Show notes

pip is the package installer for Python.

Often, when you run pip, especially the first time in a new virtual environment, you will see something like:

WARNING: You are using pip version 20.1.1; however, version 20.2 is available.

You should consider upgrading via the 'python -m pip install --upgrade pip' command.

And you should. Because 20.2 has a new dependency resolver.

Get in the habit, until October, of replacing pip install with pip install --use-feature=2020-resolver.

This flag is new in the 20.2 release.

This new pip dependency resolver is the result of a lot of work.

Five of the people involved with this work are joining the show today: Bernard Tyers, Nicole Harris, Paul Moore, Pradyun Gedam, and Tzu-ping Chung.

We talk about:

pip dependency resolver changes
user experience research and testing
crafting good error messages
efforts to improve the test suite
testing pip with pytest
some of the difficulties with testing pip
working with a team on a large project
working with a large code base
bringing new developers into a large project

Special Guests: Bernard Tyers, Nicole Harris, Paul Moore, Pradyun Gedam, and Tzu-ping Chung.

Links:

Changelog — pip 20.2 documentation — Including --use-feature=2020-resolver
pypa/pip: The Python package installer — github repo
testing pip - documentation
pip - The Python Package Installer — pip 20.2 documentation
Changes to the pip dependency resolver in 20.2 — Changes to the pip dependency resolver in 20.2

123: GitHub Actions - Tania Allard Jul 24, 2020

Show notes

Lots of Python projects are starting to use GitHub Actions for Continous Integration & Deployment (CI/CD), as well as other workflows.

Tania Allard, a Senior Cloud Developer Advocate at Microsoft, joins the show to answer some of my questions regarding setting up a Python project to use Actions.

Some of the topics covered:

How to get started with GitHub Actions for a Python project?
What are workflow files?
Does it matter what the file name is called?
Can I have / Should I have more than one workflow?

Special Guest: Tania Allard.

Links:

Using Python with GitHub Actions - GitHub Docs
awesome-actions — A curated list of awesome actions to use on GitHub

122: Better Resumes for Software Engineers - Randall Kanna Jul 16, 2020

Show notes

A great resume is key to landing a great software job.
There's no surprise there.
But so many people make mistakes on their resume that can very easily be fixed.

Randall Kanna is on the show today to help us understand how to improve our resumes, and in turn, help us have better careers.

Special Guest: Randall Kanna.

Links:

The Standout Developer — link includes discount

121: Industrial 3D Printing & Python, Finite State Machines, and Simulating Hardware - Len Wanger Jul 09, 2020

Show notes

Len Wanger works on industrial 3D printers. And I was pleased to find out that
there's a bunch of Python in those printers as well.

In this episode we talk about:

3D printers
What are the different types of 3D printers?
Where are 3D printed industrial parts being used?
Why use one type of additive manufacturing over another?
Python in 3D printing hardware.
What are Finite State Machines, FSMs?
Benefits of FSMs for testing, logging, and breaking a complex behavior into small testable parts.
Benefits of simulation in writing and testing software to control hardware.

Special Guest: Len Wanger.

Links:

pystate — Python package for co-routine base state machines
Impossible Objects — Composite 3D Printing
Finite-state machine, FSM

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