pytest-param-files

A small package to generate parametrized pytests from external files.

Simply create a text file with an available format:

dot format (default):

[name1] description
.
input content
.
expected output content
.

[name2] description
.
input content
.
expected output content
.

yaml format:

name1:
  description: optional description
  input: |-
    input content
  expected: |-
    expected output content
name2:
  description: optional description
  input: |-
    input content
  expected: |-
    expected output content

Then, use the param_file pytest marker to create a parametrized test:

from pathlib import Path
import pytest

import my_function

PATH = Path(__file__).parent.joinpath("test_file.txt")

@pytest.mark.param_file(PATH, fmt="dot")
def test_function(file_params):
    assert my_function(file_params.content) == file_params.expected

and the output will be:

$ pytest -v test_file.py
...
test_file.py::test_function[1-name1] PASSED
test_file.py::test_function[8-name2] FAILED

Alternatively use the assert_expected method, which will can handle more rich assertion features:

@pytest.mark.param_file(PATH, fmt="dot")
def test_function(file_params):
    actual = my_function(file_params.content)
    assert file_params.assert_expected(actual, rstrip=True)

$ pytest -v test_file.py
...
test_file.py::test_function[1-name1] PASSED
test_file.py::test_function[8-name2] FAILED
...
E       AssertionError: Actual does not match expected
E       --- /path/to/test_file.txt:8
E       +++ (actual)
E       @@ -1 +1 @@
E       -content
E       +other

Installation

Install from PyPI:

$ pip install pytest-param-files

or install locally (for development):

$ pip install -e .

Regenerating expected output on failures

Running pytest with the --regen-file-failure option will regenerate the parameter file with actual output, if any test fails.

Note, currently regeneration of YAML files may not provide the same formatting as the original file, and will not preserve comments.

Other formats

TODO ...