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A plugin which allows to compare results with canonical results, based on previous runs

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A plugin which allows to compare results with canonical results, based on previous runs.

Inspired by Yandex’s canondata plugin, pytest-needle and pytest-regtest.

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


  • Implement pytest’s hooks for asserts

  • Use pytest’s asserts for comparing objects

  • Driver for images

  • Driver for json

  • HTML reports for images


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

$ pip install pytest-canonical-data


Plugin provides canonical_data fixture, which allows to create canonical results:

def test_sth(canonical_data):
    # creates canonical result object with name `result.txt` and `text` driver
    canonical_result = canonical_data('result.txt', 'text')
    # In default mode will compare saved canonical result with `123` string
    # In canonize mode will save `123` as the canonical result

To run in canonize mode execute:

pytest --canonize

It will create files with canonical results (if don’t exist) and save actual results.


You need to use appropriate driver for each data type. Currently, there are the following drivers:

  • bytes: for comparing bytes sequences.

  • str: for comparing python strings.

  • text: alias for the str driver.


Contributions are very welcome. Tests can be run with tox, please ensure the coverage at least stays the same before you submit a pull request.


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


If you encounter any problems, please file an issue along with a detailed description.

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