Run pytest against a specific Python version using Docker#

For datasette issue #1802 I needed to run my pytest test suite using a specific version of Python 3.7.

I decided to do this using Docker, using the official python:3.7-buster image.

Here’s the recipe that worked for me:

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docker run --rm -it -v `pwd`:/code \
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  python:3.7-buster \
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  bash -c "cd /code && pip install -e '.[test]' && pytest"

This command runs interactively so I can see the output (the -it option).

It mounts the current directory (with my testable application in it - I ran this in the root of a datasette checkout) as the /code volume inside the container.

The --rm option ensures that the container used for the test will be deleted once the test has completed (not just stopped).

It then runs the following using bash -c:

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cd /code && pip install -e '.[test]' && pytest

This installs my project’s dependencies and test dependencies and then runs pytest.

The truncated output looks like this:

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% docker run -it -v `pwd`:/code \
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  python:3.7-buster \
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  bash -c "cd /code && pip install -e '.[test]' && pytest"
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Obtaining file:///code
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  Preparing metadata (setup.py) ... done
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Collecting asgiref>=3.2.10
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  Downloading asgiref-3.5.2-py3-none-any.whl (22 kB)
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...
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Installing collected packages: rfc3986, mypy-extensions, iniconfig, zipp, typing-extensions, typed-ast, tomli, soupsieve, sniffio, six, PyYAML, pyparsing, pycparser, py, platformdirs, pathspec, mergedeep, MarkupSafe, itsdangerous, idna, hupper, h11, execnet, cogapp, certifi, attrs, aiofiles, python-multipart, packaging, Jinja2, janus, importlib-metadata, cffi, beautifulsoup4, asgiref, anyio, pluggy, pint, httpcore, cryptography, click, asgi-csrf, uvicorn, trustme, pytest, httpx, click-default-group-wheel, black, pytest-timeout, pytest-forked, pytest-asyncio, datasette, blacken-docs, pytest-xdist
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  Running setup.py develop for datasette
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...
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========================================================= test session starts ==========================================================
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platform linux -- Python 3.7.13, pytest-7.1.3, pluggy-1.0.0
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SQLite: 3.27.2
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rootdir: /code, configfile: pytest.ini
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plugins: asyncio-0.19.0, anyio-3.6.1, timeout-2.1.0, xdist-2.5.0, forked-1.4.0
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asyncio: mode=strict
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collected 1054 items
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tests/test_package.py ..                                                                                                         [  0%]
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tests/test_cli.py .                                                                                                              [  0%]
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tests/test_cli_serve_get.py ..                                                                                                   [  0%]
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tests/test_cli.py .                                                                                                              [  0%]
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tests/test_black.py .                                                                                                            [  0%]
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tests/test_api.py ..................................................                                                             [  5%]

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Run pytest against a specific Python version using Docker#