pytest / doc / en / usage.txt

.. _usage:

Usage and Invocations
==========================================


.. _cmdline:

Calling pytest through ``python -m pytest``
-----------------------------------------------------

.. versionadded:: 2.0

If you use Python-2.5 or later you can invoke testing through the
Python interpreter from the command line::

    python -m pytest [...]

This is equivalent to invoking the command line script ``py.test [...]``
directly.

Getting help on version, option names, environment variables
--------------------------------------------------------------

::

    py.test --version   # shows where pytest was imported from
    py.test --fixtures  # show available builtin function arguments
    py.test -h | --help # show help on command line and config file options


Stopping after the first (or N) failures
---------------------------------------------------

To stop the testing process after the first (N) failures::

    py.test -x            # stop after first failure
    py.test --maxfail=2    # stop after two failures

Specifying tests / selecting tests
---------------------------------------------------

Several test run options::

    py.test test_mod.py   # run tests in module
    py.test somepath      # run all tests below path
    py.test -k string     # only run tests whose names contain a string

Import 'pkg' and use its filesystem location to find and run tests::

    py.test --pyargs pkg # run all tests found below directory of pypkg

Modifying Python traceback printing
----------------------------------------------

Examples for modifying traceback printing::

    py.test --showlocals # show local variables in tracebacks
    py.test -l           # show local variables (shortcut)

    py.test --tb=long    # the default informative traceback formatting
    py.test --tb=native  # the Python standard library formatting
    py.test --tb=short   # a shorter traceback format
    py.test --tb=line    # only one line per failure

Dropping to PDB (Python Debugger) on failures
----------------------------------------------

.. _PDB: http://docs.python.org/library/pdb.html

Python comes with a builtin Python debugger called PDB_.  ``py.test``
allows one to drop into the PDB prompt via a command line option::

    py.test --pdb

This will invoke the Python debugger on every failure.  Often you might
only want to do this for the first failing test to understand a certain
failure situation::

    py.test -x --pdb   # drop to PDB on first failure, then end test session
    py.test --pdb --maxfail=3  # drop to PDB for the first three failures


Setting a breakpoint / aka ``set_trace()``
----------------------------------------------------

If you want to set a breakpoint and enter the ``pdb.set_trace()`` you
can use a helper::

    import pytest
    def test_function():
        ...
        pytest.set_trace()    # invoke PDB debugger and tracing

.. versionadded: 2.0.0

In previous versions you could only enter PDB tracing if
you disabled capturing on the command line via ``py.test -s``.

.. _durations:

Profiling test execution duration
-------------------------------------

.. versionadded: 2.2

To get a list of the slowest 10 test durations::

    py.test --durations=10


Creating JUnitXML format files
----------------------------------------------------

To create result files which can be read by Hudson_ or other Continuous
integration servers, use this invocation::

    py.test --junitxml=path

to create an XML file at ``path``.

Creating resultlog format files
----------------------------------------------------

To create plain-text machine-readable result files you can issue::

    py.test --resultlog=path

and look at the content at the ``path`` location.  Such files are used e.g.
by the `PyPy-test`_ web page to show test results over several revisions.

.. _`PyPy-test`: http://buildbot.pypy.org/summary


Sending test report to online pastebin service
-----------------------------------------------------

**Creating a URL for each test failure**::

    py.test --pastebin=failed

This will submit test run information to a remote Paste service and
provide a URL for each failure.  You may select tests as usual or add
for example ``-x`` if you only want to send one particular failure.

**Creating a URL for a whole test session log**::

    py.test --pastebin=all

Currently only pasting to the http://bpaste.net service is implemented.

.. _`pytest.main-usage`:

Calling pytest from Python code
----------------------------------------------------

.. versionadded:: 2.0

You can invoke ``py.test`` from Python code directly::

    pytest.main()

this acts as if you would call "py.test" from the command line.
It will not raise ``SystemExit`` but return the exitcode instead.
You can pass in options and arguments::

    pytest.main(['x', 'mytestdir'])

or pass in a string::

    pytest.main("-x mytestdir")

You can specify additional plugins to ``pytest.main``::

    # content of myinvoke.py
    import pytest
    class MyPlugin:
        def pytest_sessionfinish(self):
            print("*** test run reporting finishing")

    pytest.main("-qq", plugins=[MyPlugin()])

Running it will show that ``MyPlugin`` was added and its
hook was invoked::

    $ python myinvoke.py
    
    *** test run reporting finishing

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