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pytest-watch – Continuous pytest runner

Current version on PyPI Say Thanks!

pytest-watch a zero-config CLI tool that runs pytest, and re-runs it when a file in your project changes. It beeps on failures and can run arbitrary commands on each passing and failing test run.

Motivation

Whether or not you use the test-driven development method, running tests continuously is far more productive than waiting until you’re finished programming to test your code. Additionally, manually running pytest each time you want to see if any tests were broken has more wait-time and cognitive overhead than merely listening for a notification. This could be a crucial difference when debugging a complex problem or on a tight deadline.

Installation

$ pip install pytest-watch

Usage

$ cd myproject
$ ptw
 * Watching /path/to/myproject

Note: It can also be run using its full name ``pytest-watch``.

Now develop normally and check the terminal every now and then to see if any tests are broken. Alternatively, pytest-watch can notify you when tests pass or fail:

  • OSX

    $ ptw --onpass "say passed" --onfail "say failed"

    $ ptw --onpass "growlnotify -m \"All tests passed!\"" \
      --onfail "growlnotify -m \"Tests failed\""

    using GrowlNotify.

  • Windows

    > ptw --onfail flash

    using Console Flash

You can also run a command before the tests run, e.g. seeding your test database:

$ ptw --beforerun init_db.py

Or after they finish, e.g. deleting a sqlite file. Note that this script receives the exit code of pytest as an argument.

$ ptw --afterrun cleanup_db.py

You can also use a custom runner script for full pytest control:

$ ptw --runner "python custom_pytest_runner.py"

Here’s an minimal runner script that runs pytest and prints its exit code:

# custom_pytest_runner.py

import sys
import pytest

print('pytest exited with code:', pytest.main(sys.argv[1:]))

Need to exclude directories from being observed or collected for tests?

$ ptw --ignore ./deep-directory --ignore ./integration_tests

See the full list of options:

$ ptw --help
Usage: ptw [options] [--ignore <dir>...] [<directory>...] [-- <pytest-args>...]

Options:
  --ignore <dir>        Ignore directory from being watched and during
                        collection (multi-allowed).
  --ext <exts>          Comma-separated list of file extensions that can
                        trigger a new test run when changed (default: .py).
                        Use --ext=* to allow any file (including .pyc).
  --config <file>       Load configuration from `file` instead of trying to
                        locate one of the implicit configuration files.
  -c --clear            Clear the screen before each run.
  -n --nobeep           Do not beep on failure.
  -w --wait             Waits for all tests to complete before re-running.
                        Otherwise, tests are interrupted on filesystem events.
  --beforerun <cmd>     Run arbitrary command before tests are run.
  --afterrun <cmd>      Run arbitrary command on completion or interruption.
                        The exit code of "pytest" is passed as an argument.
  --onpass <cmd>        Run arbitrary command on pass.
  --onfail <cmd>        Run arbitrary command on failure.
  --onexit <cmd>        Run arbitrary command when exiting pytest-watch.
  --runner <cmd>        Run a custom command instead of "pytest".
  --pdb                 Start the interactive Python debugger on errors.
                        This also enables --wait to prevent pdb interruption.
  --spool <delay>       Re-run after a delay (in milliseconds), allowing for
                        more file system events to queue up (default: 200 ms).
  -p --poll             Use polling instead of OS events (useful in VMs).
  -v --verbose          Increase verbosity of the output.
  -q --quiet            Decrease verbosity of the output (precedence over -v).
  -V --version          Print version and exit.
  -h --help             Print help and exit.

Configuration

CLI options can be added to a [pytest-watch] section in your pytest.ini file to persist them in your project. For example:

# pytest.ini

[pytest]
addopts = --maxfail=2


[pytest-watch]
ignore = ./integration-tests
nobeep = True

Alternatives

  • xdist offers the --looponfail (-f) option (and distributed testing options). This instead re-runs only those tests which have failed until you make them pass. This can be a speed advantage when trying to get all tests passing, but leaves out the discovery of new failures until then. It also drops the colors outputted by pytest, whereas pytest-watch doesn’t.
  • Nosey is the original codebase this was forked from. Nosey runs nose instead of pytest.

Contributing

  1. Check the open issues or open a new issue to start a discussion around your feature idea or the bug you found
  2. Fork the repository, make your changes, and add yourself to Authors.md
  3. Send a pull request

If you want to edit the README, be sure to make your changes to README.md and run the following to regenerate the README.rst file:

$ pandoc -t rst -o README.rst README.md

If your PR has been waiting a while, feel free to ping me on Twitter.

Use this software often? 😃