src/third_party/web_platform_tests/tools/pytest/doc/en/xdist.rst - cobalt - Git at Google


 .. _`xdist`:

 xdist: pytest distributed testing plugin
 ===============================================================

 The `pytest-xdist`_ plugin extends ``pytest`` with some unique
 test execution modes:

 * Looponfail: run your tests repeatedly in a subprocess.  After each
   run, ``pytest`` waits until a file in your project changes and then
   re-runs the previously failing tests.  This is repeated until all
   tests pass.  At this point a full run is again performed.

 * multiprocess Load-balancing: if you have multiple CPUs or hosts you can use
   them for a combined test run.  This allows to speed up
   development or to use special resources of remote machines.

 * Multi-Platform coverage: you can specify different Python interpreters
   or different platforms and run tests in parallel on all of them.

 Before running tests remotely, ``pytest`` efficiently "rsyncs" your
 program source code to the remote place.  All test results
 are reported back and displayed to your local terminal.
 You may specify different Python versions and interpreters.


 Installation of xdist plugin
 ------------------------------

 Install the plugin with::

     easy_install pytest-xdist

     # or

     pip install pytest-xdist

 or use the package in develop/in-place mode with
 a checkout of the `pytest-xdist repository`_ ::

     python setup.py develop


 Usage examples
 ---------------------

 .. _`xdistcpu`:

 Speed up test runs by sending tests to multiple CPUs
 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

 To send tests to multiple CPUs, type::

     py.test -n NUM

 Especially for longer running tests or tests requiring
 a lot of I/O this can lead to considerable speed ups.


 Running tests in a Python subprocess
 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

 To instantiate a Python-2.7 subprocess and send tests to it, you may type::

     py.test -d --tx popen//python=python2.7

 This will start a subprocess which is run with the "python2.7"
 Python interpreter, found in your system binary lookup path.

 If you prefix the --tx option value like this::

     py.test -d --tx 3*popen//python=python2.7

 then three subprocesses would be created and the tests
 will be distributed to three subprocesses and run simultanously.

 .. _looponfailing:


 Running tests in looponfailing mode
 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

 For refactoring a project with a medium or large test suite
 you can use the looponfailing mode. Simply add the ``--f`` option::

     py.test -f

 and ``pytest`` will run your tests. Assuming you have failures it will then
 wait for file changes and re-run the failing test set.  File changes are detected by looking at ``looponfailingroots`` root directories and all of their contents (recursively).  If the default for this value does not work for you you
 can change it in your project by setting a configuration option::

     # content of a pytest.ini, setup.cfg or tox.ini file
     [pytest]
     looponfailroots = mypkg testdir

 This would lead to only looking for file changes in the respective directories, specified relatively to the ini-file's directory.

 Sending tests to remote SSH accounts
 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

 Suppose you have a package ``mypkg`` which contains some
 tests that you can successfully run locally. And you also
 have a ssh-reachable machine ``myhost``.  Then
 you can ad-hoc distribute your tests by typing::

     py.test -d --tx ssh=myhostpopen --rsyncdir mypkg mypkg

 This will synchronize your ``mypkg`` package directory
 with a remote ssh account and then collect and run your
 tests at the remote side.

 You can specify multiple ``--rsyncdir`` directories
 to be sent to the remote side.

 .. XXX CHECK

     **NOTE:** For ``pytest`` to collect and send tests correctly
     you not only need to make sure all code and tests
     directories are rsynced, but that any test (sub) directory
     also has an ``__init__.py`` file because internally
     ``pytest`` references tests as a fully qualified python
     module path.  **You will otherwise get strange errors**
     during setup of the remote side.

 Sending tests to remote Socket Servers
 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

 Download the single-module `socketserver.py`_ Python program
 and run it like this::

     python socketserver.py

 It will tell you that it starts listening on the default
 port.  You can now on your home machine specify this
 new socket host with something like this::

     py.test -d --tx socket=192.168.1.102:8888 --rsyncdir mypkg mypkg


 .. _`atonce`:

 Running tests on many platforms at once
 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

 The basic command to run tests on multiple platforms is::

     py.test --dist=each --tx=spec1 --tx=spec2

 If you specify a windows host, an OSX host and a Linux
 environment this command will send each tests to all
 platforms - and report back failures from all platforms
 at once.   The specifications strings use the `xspec syntax`_.

 .. _`xspec syntax`: http://codespeak.net/execnet/basics.html#xspec

 .. _`socketserver.py`: http://bitbucket.org/hpk42/execnet/raw/2af991418160/execnet/script/socketserver.py

 .. _`execnet`: http://codespeak.net/execnet

 Specifying test exec environments in an ini file
 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

 pytest (since version 2.0) supports ini-style configuration.
 For example, you could make running with three subprocesses your default::

     [pytest]
     addopts = -n3

 You can also add default environments like this::

     [pytest]
     addopts = --tx ssh=myhost//python=python2.7 --tx ssh=myhost//python=python2.6

 and then just type::

     py.test --dist=each

 to run tests in each of the environments.

 Specifying "rsync" dirs in an ini-file
 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

 In a ``tox.ini`` or ``setup.cfg`` file in your root project directory
 you may specify directories to include or to exclude in synchronisation::

     [pytest]
     rsyncdirs = . mypkg helperpkg
     rsyncignore = .hg

 These directory specifications are relative to the directory
 where the configuration file was found.

 .. _`pytest-xdist`: http://pypi.python.org/pypi/pytest-xdist
 .. _`pytest-xdist repository`: http://bitbucket.org/pytest-dev/pytest-xdist
 .. _`pytest`: http://pytest.org

	.. _`xdist`:

	xdist: pytest distributed testing plugin
	===============================================================

	The `pytest-xdist`_ plugin extends ``pytest`` with some unique
	test execution modes:

	* Looponfail: run your tests repeatedly in a subprocess. After each
	run, ``pytest`` waits until a file in your project changes and then
	re-runs the previously failing tests. This is repeated until all
	tests pass. At this point a full run is again performed.

	* multiprocess Load-balancing: if you have multiple CPUs or hosts you can use
	them for a combined test run. This allows to speed up
	development or to use special resources of remote machines.

	* Multi-Platform coverage: you can specify different Python interpreters
	or different platforms and run tests in parallel on all of them.

	Before running tests remotely, ``pytest`` efficiently "rsyncs" your
	program source code to the remote place. All test results
	are reported back and displayed to your local terminal.
	You may specify different Python versions and interpreters.


	Installation of xdist plugin
	------------------------------

	Install the plugin with::

	easy_install pytest-xdist

	# or

	pip install pytest-xdist

	or use the package in develop/in-place mode with
	a checkout of the `pytest-xdist repository`_ ::

	python setup.py develop


	Usage examples
	---------------------

	.. _`xdistcpu`:

	Speed up test runs by sending tests to multiple CPUs
	+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

	To send tests to multiple CPUs, type::

	py.test -n NUM

	Especially for longer running tests or tests requiring
	a lot of I/O this can lead to considerable speed ups.


	Running tests in a Python subprocess
	+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

	To instantiate a Python-2.7 subprocess and send tests to it, you may type::

	py.test -d --tx popen//python=python2.7

	This will start a subprocess which is run with the "python2.7"
	Python interpreter, found in your system binary lookup path.

	If you prefix the --tx option value like this::

	py.test -d --tx 3*popen//python=python2.7

	then three subprocesses would be created and the tests
	will be distributed to three subprocesses and run simultanously.

	.. _looponfailing:


	Running tests in looponfailing mode
	+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

	For refactoring a project with a medium or large test suite
	you can use the looponfailing mode. Simply add the ``--f`` option::

	py.test -f

	and ``pytest`` will run your tests. Assuming you have failures it will then
	wait for file changes and re-run the failing test set. File changes are detected by looking at ``looponfailingroots`` root directories and all of their contents (recursively). If the default for this value does not work for you you
	can change it in your project by setting a configuration option::

	# content of a pytest.ini, setup.cfg or tox.ini file
	[pytest]
	looponfailroots = mypkg testdir

	This would lead to only looking for file changes in the respective directories, specified relatively to the ini-file's directory.

	Sending tests to remote SSH accounts
	+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

	Suppose you have a package ``mypkg`` which contains some
	tests that you can successfully run locally. And you also
	have a ssh-reachable machine ``myhost``. Then
	you can ad-hoc distribute your tests by typing::

	py.test -d --tx ssh=myhostpopen --rsyncdir mypkg mypkg

	This will synchronize your ``mypkg`` package directory
	with a remote ssh account and then collect and run your
	tests at the remote side.

	You can specify multiple ``--rsyncdir`` directories
	to be sent to the remote side.

	.. XXX CHECK

	NOTE: For ``pytest`` to collect and send tests correctly
	you not only need to make sure all code and tests
	directories are rsynced, but that any test (sub) directory
	also has an ``__init__.py`` file because internally
	``pytest`` references tests as a fully qualified python
	module path. You will otherwise get strange errors
	during setup of the remote side.

	Sending tests to remote Socket Servers
	+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

	Download the single-module `socketserver.py`_ Python program
	and run it like this::

	python socketserver.py

	It will tell you that it starts listening on the default
	port. You can now on your home machine specify this
	new socket host with something like this::

	py.test -d --tx socket=192.168.1.102:8888 --rsyncdir mypkg mypkg


	.. _`atonce`:

	Running tests on many platforms at once
	+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

	The basic command to run tests on multiple platforms is::

	py.test --dist=each --tx=spec1 --tx=spec2

	If you specify a windows host, an OSX host and a Linux
	environment this command will send each tests to all
	platforms - and report back failures from all platforms
	at once. The specifications strings use the `xspec syntax`_.

	.. _`xspec syntax`: http://codespeak.net/execnet/basics.html#xspec

	.. _`socketserver.py`: http://bitbucket.org/hpk42/execnet/raw/2af991418160/execnet/script/socketserver.py

	.. _`execnet`: http://codespeak.net/execnet

	Specifying test exec environments in an ini file
	+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

	pytest (since version 2.0) supports ini-style configuration.
	For example, you could make running with three subprocesses your default::

	[pytest]
	addopts = -n3

	You can also add default environments like this::

	[pytest]
	addopts = --tx ssh=myhost//python=python2.7 --tx ssh=myhost//python=python2.6

	and then just type::

	py.test --dist=each

	to run tests in each of the environments.

	Specifying "rsync" dirs in an ini-file
	+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

	In a ``tox.ini`` or ``setup.cfg`` file in your root project directory
	you may specify directories to include or to exclude in synchronisation::

	[pytest]
	rsyncdirs = . mypkg helperpkg
	rsyncignore = .hg

	These directory specifications are relative to the directory
	where the configuration file was found.

	.. _`pytest-xdist`: http://pypi.python.org/pypi/pytest-xdist
	.. _`pytest-xdist repository`: http://bitbucket.org/pytest-dev/pytest-xdist
	.. _`pytest`: http://pytest.org