Temporary file hierarchies for pytest

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pytest_tmp_files is a pytest plugin that provides a fixture for creating temporary file hierarchies. This fixture is called tmp_files, and you can think of it as an extension of the built-in tmp_path fixture. In addition to creating a unique temporary directory for each test, tmp_files also fills in that directory with any files needed for that test.

The files to create are specified by a dictionary provided to fixture via indirect parametrization. For example, here’s a test for a function that searches for files whose contents match a given regular expression:

import pytest, re
from pathlib import Path

def find_text(top, pattern):
    hits = set()

    for path in Path(top).glob('**/*'):
        if path.is_file() and re.search(pattern, path.read_text()):

    return hits

    'tmp_files, pattern, expected', [
        ({'a': 'x'}, 'x', {'a'}),
        ({'a': 'x'}, 'y', set()),
        ({'a/b': 'x'}, 'x', {'a/b'}),
        ({'a/b': 'x'}, 'y', set()),
        ({'a/b': 'x', 'c': 'y'}, 'x', {'a/b'}),
        ({'a/b': 'x', 'c': 'y'}, 'y', {'c'}),
        ({'a/b': 'x', 'c': 'y'}, '[xy]', {'a/b', 'c'}),
def test_find_text(tmp_files, pattern, expected):
    expected = {
            tmp_files / p
            for p in expected
    assert find_text(tmp_files, pattern) == expected

The first parameter in each set (the dictionary) specifies the files to create. The keys are file paths and the values are file contents, so {'a/b': 'x'} specifies a subdirectory a containing a text file b with the contents x. Although not shown here, it’s also possible to create different kinds of files (e.g. binary files, symlinks, hard links, named FIFOs) and to specify file metadata (e.g. permissions, modification times). See the documentation for details.