Temporary directories and files — pytest documentation (original) (raw)

The tmp_path fixture¶

You can use the tmp_path fixture which will provide a temporary directory unique to the test invocation, created in the base temporary directory.

tmp_path is a pathlib.Path object. Here is an example test usage:

content of test_tmp_path.py

CONTENT = "content"

def test_create_file(tmp_path): d = tmp_path / "sub" d.mkdir() p = d / "hello.txt" p.write_text(CONTENT) assert p.read_text() == CONTENT assert len(list(tmp_path.iterdir())) == 1 assert 0

Running this would result in a passed test except for the lastassert 0 line which we use to look at values:

$ pytest test_tmp_path.py =========================== test session starts ============================ platform linux -- Python 3.x.y, pytest-6.x.y, py-1.x.y, pluggy-1.x.y cachedir: $PYTHON_PREFIX/.pytest_cache rootdir: $REGENDOC_TMPDIR collected 1 item

test_tmp_path.py F [100%]

================================= FAILURES ================================= _____________________________ test_create_file _____________________________

tmp_path = PosixPath('PYTEST_TMPDIR/test_create_file0')

def test_create_file(tmp_path):
    d = tmp_path / "sub"
    d.mkdir()
    p = d / "hello.txt"
    p.write_text(CONTENT)
    assert p.read_text() == CONTENT
    assert len(list(tmp_path.iterdir())) == 1

  assert 0

E assert 0

test_tmp_path.py:11: AssertionError ========================= short test summary info ========================== FAILED test_tmp_path.py::test_create_file - assert 0 ============================ 1 failed in 0.12s =============================

The tmp_path_factory fixture¶

The tmp_path_factory is a session-scoped fixture which can be used to create arbitrary temporary directories from any other fixture or test.

It is intended to replace tmpdir_factory, and returns pathlib.Path instances.

See tmp_path_factory API for details.

The ‘tmpdir’ fixture¶

You can use the tmpdir fixture which will provide a temporary directory unique to the test invocation, created in the base temporary directory.

tmpdir is a py.path.local object which offers os.path methods and more. Here is an example test usage:

content of test_tmpdir.py

def test_create_file(tmpdir): p = tmpdir.mkdir("sub").join("hello.txt") p.write("content") assert p.read() == "content" assert len(tmpdir.listdir()) == 1 assert 0

Running this would result in a passed test except for the lastassert 0 line which we use to look at values:

$ pytest test_tmpdir.py =========================== test session starts ============================ platform linux -- Python 3.x.y, pytest-6.x.y, py-1.x.y, pluggy-1.x.y cachedir: $PYTHON_PREFIX/.pytest_cache rootdir: $REGENDOC_TMPDIR collected 1 item

test_tmpdir.py F [100%]

================================= FAILURES ================================= _____________________________ test_create_file _____________________________

tmpdir = local('PYTEST_TMPDIR/test_create_file0')

def test_create_file(tmpdir):
    p = tmpdir.mkdir("sub").join("hello.txt")
    p.write("content")
    assert p.read() == "content"
    assert len(tmpdir.listdir()) == 1

  assert 0

E assert 0

test_tmpdir.py:6: AssertionError ========================= short test summary info ========================== FAILED test_tmpdir.py::test_create_file - assert 0 ============================ 1 failed in 0.12s =============================

The ‘tmpdir_factory’ fixture¶

The tmpdir_factory is a session-scoped fixture which can be used to create arbitrary temporary directories from any other fixture or test.

For example, suppose your test suite needs a large image on disk, which is generated procedurally. Instead of computing the same image for each test that uses it into its own tmpdir, you can generate it once per-session to save time:

contents of conftest.py

import pytest

@pytest.fixture(scope="session") def image_file(tmpdir_factory): img = compute_expensive_image() fn = tmpdir_factory.mktemp("data").join("img.png") img.save(str(fn)) return fn

contents of test_image.py

def test_histogram(image_file): img = load_image(image_file) # compute and test histogram

See tmpdir_factory API for details.

The default base temporary directory¶

Temporary directories are by default created as sub-directories of the system temporary directory. The base name will be pytest-NUM whereNUM will be incremented with each test run. Moreover, entries older than 3 temporary directories will be removed.

You can override the default temporary directory setting like this:

Warning

The contents of mydir will be completely removed, so make sure to use a directory for that purpose only.

When distributing tests on the local machine using pytest-xdist, care is taken to automatically configure a basetemp directory for the sub processes such that all temporary data lands below a single per-test run basetemp directory.