.. _`pytest helpers`:

Pytest builtin helpers
================================================

builtin pytest.* functions and helping objects
-----------------------------------------------------

You can always use an interactive Python prompt and type::

    import pytest
    help(pytest)

to get an overview on the globally available helpers.

.. automodule:: pytest
    :members:


.. _builtinfuncargs:

Builtin function arguments
-----------------------------------------------------

You can ask for available builtin or project-custom
:ref:`function arguments <funcargs>` by typing::

    $ py.test --funcargs
    =========================== test session starts ============================
    platform darwin -- Python 2.7.1 -- pytest-2.2.2
    collected 0 items
    pytestconfig
        the pytest config object with access to command line opts.
    capsys
        enables capturing of writes to sys.stdout/sys.stderr and makes
        captured output available via ``capsys.readouterr()`` method calls
        which return a ``(out, err)`` tuple.
        
    capfd
        enables capturing of writes to file descriptors 1 and 2 and makes
        captured output available via ``capsys.readouterr()`` method calls
        which return a ``(out, err)`` tuple.
        
    tmpdir
        return a temporary directory path object
        which is unique to each test function invocation,
        created as a sub directory of the base temporary
        directory.  The returned object is a `py.path.local`_
        path object.
        
    monkeypatch
        The returned ``monkeypatch`` funcarg provides these
        helper methods to modify objects, dictionaries or os.environ::
        
        monkeypatch.setattr(obj, name, value, raising=True)
        monkeypatch.delattr(obj, name, raising=True)
        monkeypatch.setitem(mapping, name, value)
        monkeypatch.delitem(obj, name, raising=True)
        monkeypatch.setenv(name, value, prepend=False)
        monkeypatch.delenv(name, value, raising=True)
        monkeypatch.syspath_prepend(path)
        monkeypatch.chdir(path)
        
        All modifications will be undone after the requesting
        test function has finished. The ``raising``
        parameter determines if a KeyError or AttributeError
        will be raised if the set/deletion operation has no target.
        
    recwarn
        Return a WarningsRecorder instance that provides these methods:
        
        * ``pop(category=None)``: return last warning matching the category.
        * ``clear()``: clear list of warnings
        
        See http://docs.python.org/library/warnings.html for information
        on warning categories.
        
    cov
        A pytest funcarg that provides access to the underlying coverage object.
    
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