How do you properly integrate unit tests for file parsing with pytest?

Question

I'm trying to test file parsing with pytest. I have a directory tree that looks something like this for my project:

project
    project/
        cool_code.py
    setup.py
    setup.cfg
    test/
        test_read_files.py
        test_files/
            data_file1.txt
            data_file2.txt

My setup.py file looks something like this:

from setuptools import setup

setup(
    name           = 'project',
    description    = 'The coolest project ever!',
    setup_requires = ['pytest-runner'],
    tests_require  = ['pytest'],
    )

My setup.cfg file looks something like this:

[aliases]
test=pytest

I've written several unit tests with pytest to verify that files are properly read. They work fine when I run pytest from within the "test" directory. However, if I execute any of the following from my project directory, the tests fail because they cannot find data files in test_files:

>> py.test
>> python setup.py pytest

The test seems to be sensitive to the directory from which pytest is executed.

How can I get pytest unit tests to discover the files in "data_files" for parsing when I call it from either the test directory or the project root directory?

Answer 1

One solution is to define a rootdir fixture with the path to the test directory, and reference all data files relative to this. This can be done by creating a test/conftest.py (if not already created) with some code like this:

import os
import pytest

@pytest.fixture
def rootdir():
    return os.path.dirname(os.path.abspath(__file__))

Then use os.path.join in your tests to get absolute paths to test files:

import os

def test_read_favorite_color(rootdir):
    test_file = os.path.join(rootdir, 'test_files/favorite_color.csv')
    data = read_favorite_color(test_file)
    # ...