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pytest plugin to instrument tests

Project description

PyPI version Python versions PyPI - Downloads See Build Status on Circle CI MIT license

A pytest plugin to instrument tests and write the resulting records to file


  • a log file with one record for each setup/call/teardown of each test containing:

    • session id and record id (UUIDs generated by plugin)

    • node_id (pytest’s nodeid)

    • when (setup, call or teardown)

    • outcome (passed, failed or skipped)

    • start, stop and duration

    • labels (array) and tags (object) via @pytest.mark.instrument() decorator

    • fixtures

  • hooks to edit labels, tags and fixtures before the record is written to file

  • a logger to emit records with session id, record id, node id to the same log file


  • Python 3.6 or higher

  • pytest 5.1.0 or higher


You can install “pytest-instrument” via pip from PyPI:

$ pip install pytest-instrument


Run your tests with:

$ pytest --instrument=json

An ./artifacts directory will be created if it doesn’t exist yet. For each pytest session one .json file will be written to that directory. The format of the filename is %Y%m%dT%H%M%S_<first group of session id>.json.

To display the contents of the .log file, use jq: jq . <filename>. Or, if for instance you only want to see the message object of each record: jq '{message: .message}' <filename>

Output to regular log file

If you want to output a regular log file, use –instrument=log (or –instrument=json,log if you want both). Note that the regular log file only contains the time, log node name, log level, test node id and log message of each log record.

Loggers - instr.log and

The logger reporting on the outcome of pytest’s setup, call and teardown is named “”.

The logger emitting records to the same file as the “” logger is named “instr.log”. You can use this logger like this:

logger = logging.getLogger("instr.log")"log record of level info")

You can also create children of that logger, which will emit records to that same file:

sublogger = logging.getLogger("instr.log").getChild("sublogger")
logger.warning("log record of level warning")

The session id and node id of the “instr.log” logger and its children are set automatically in the getChild() method. The node id is updated automatically via pytests’s pytest_runtest_setup() hook.

Labels and tags

You can add labels and tags to tests with the plugin’s mark decorator:

@pytest.mark.instrument("a_label", my_tag="tagged")

All args, such as "a_label", are put in the json array labels. All kwargs, such as my_tag="tagged", are put in the json object tags.


  • pytest_instrument_labels: edit list of labels after they’ve been parsed by the plugin

  • pytest_instrument_tags: edit dictionary of tags after they’ve been parsed by the plugin

  • pytest_instrument_fixtures: edit list of fixtures after they’ve been parsed by the plugin


Consult the changelog for fixes and enhancements of each version.


Please use the GitHub issue tracker to submit bugs or request features.


Contributions are welcome. Tests can be run with tox, please ensure black code formatting and good test coverage before you submit a pull request.


Distributed under the terms of the MIT license, “pytest-instrument” is free and open source software


Thank you to Maaret Pyhäjärvi for inspiring this plugin by sharing the story of how her team started instrumenting tests at TestCraftCamp 2019.

Thank you to Tony S Yu for backporting the stacklevel argument from Python 3.8 logging.

This pytest plugin was generated with Cookiecutter along with @hackebrot’s cookiecutter-pytest-plugin template.

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