test_ok2/doc/tmpdir.txt

temporary directories and files
================================================

the 'tmpdir' test function argument
-----------------------------------

You can use the ``tmpdir`` function argument 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(os.listdir(str(tmpdir))) == 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 linux2 -- Python 2.6.5 -- pytest-2.0.0dev0
    test path 1: test_tmpdir.py
    
    test_tmpdir.py F
    
    ================================= FAILURES =================================
    _____________________________ test_create_file _____________________________
    
    tmpdir = local('/tmp/pytest-427/test_create_file0')
    
        def test_create_file(tmpdir):
            p = tmpdir.mkdir("sub").join("hello.txt")
            p.write("content")
            assert p.read() == "content"
            assert len(os.listdir(str(tmpdir))) == 1
    >       assert 0
    E       assert 0
    
    test_tmpdir.py:7: AssertionError
    ========================= 1 failed in 0.03 seconds =========================

.. _`base temporary directory`:

the default base temporary directory
-----------------------------------------------

.. 
    You can create directories by calling one of two methods
    on the config object:
    - ``config.mktemp(basename)``: create and return a new tempdir
    - ``config.ensuretemp(basename)``: create or return a new tempdir

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

You can override the default temporary directory logic and set it like this::

    py.test --basetemp=mydir

When distributing tests on the local machine, ``py.test`` takes care to 
configure a basetemp directory for the sub processes such that all 
temporary data lands below below a single per-test run basetemp directory.

.. _`py.path.local`: http://pylib.org/path.html