Pytest where to store expected data

I had a similar problem once, where I have to test configuration file against an expected file. That's how I fixed it:

1. Create a folder with the same name of your test module and at the same location. Put all your expected files inside that folder.

   test_foo/
       expected_config_1.ini
       expected_config_2.ini
   test_foo.py
   

2. Create a fixture responsible for moving the contents of this folder to a temporary file. I did use of tmpdir fixture for this matter.

   from __future__ import unicode_literals
   from distutils import dir_util
   from pytest import fixture
   import os
   
   
   @fixture
   def datadir(tmpdir, request):
       '''
       Fixture responsible for searching a folder with the same name of test
       module and, if available, moving all contents to a temporary directory so
       tests can use them freely.
       '''
       filename = request.module.__file__
       test_dir, _ = os.path.splitext(filename)
   
       if os.path.isdir(test_dir):
           dir_util.copy_tree(test_dir, bytes(tmpdir))
   
       return tmpdir
   

   Important: If you are using Python 3, replace dir_util.copy_tree(test_dir, bytes(tmpdir)) with dir_util.copy_tree(test_dir, str(tmpdir)).

3. Use your new fixture.

   def test_foo(datadir):
       expected_config_1 = datadir.join('expected_config_1.ini')
       expected_config_2 = datadir.join('expected_config_2.ini')
   

Remember: datadir is just the same as tmpdir fixture, plus the ability of working with your expected files placed into the a folder with the very name of test module.

I believe pytest-datafiles can be of great help. Unfortunately, it seems not to be maintained much anymore. For the time being, it's working nicely.

Here's a simple example taken from the docs:

import os
import pytest

@pytest.mark.datafiles('/opt/big_files/film1.mp4')
def test_fast_forward(datafiles):
    path = str(datafiles)  # Convert from py.path object to path (str)
    assert len(os.listdir(path)) == 1
    assert os.path.isfile(os.path.join(path, 'film1.mp4'))
    #assert some_operation(os.path.join(path, 'film1.mp4')) == expected_result

    # Using py.path syntax
    assert len(datafiles.listdir()) == 1
    assert (datafiles / 'film1.mp4').check(file=1)