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.. _`tmpdir handling`:
.. _tmpdir:
Temporary directories and files
================================================
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
import os
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 last
``assert 0`` line which we use to look at values::
$ py.test test_tmpdir.py
======= test session starts ========
platform linux -- Python 3.4.0, pytest-2.9.1, py-1.4.31, pluggy-0.3.1
rootdir: $REGENDOC_TMPDIR, inifile:
collected 1 items
test_tmpdir.py F
======= 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:7: AssertionError
======= 1 failed in 0.12 seconds ========
The 'tmpdir_factory' fixture
----------------------------
.. versionadded:: 2.8
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:
.. code-block:: python
# 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
``tmpdir_factory`` instances have the following methods:
.. currentmodule:: _pytest.tmpdir
.. automethod:: TempdirFactory.mktemp
.. automethod:: TempdirFactory.getbasetemp
.. _`base temporary directory`:
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`` where
``NUM`` 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::
py.test --basetemp=mydir
When distributing tests on the local machine, ``pytest`` takes care to
configure a basetemp directory for the sub processes such that all temporary
data lands below a single per-test run basetemp directory.
.. _`py.path.local`: http://py.rtfd.org/en/latest/path.html
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