198 lines
6.2 KiB
ReStructuredText
198 lines
6.2 KiB
ReStructuredText
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.. _`xdist`:
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xdist: pytest distributed testing plugin
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===============================================================
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The `pytest-xdist`_ plugin extends ``pytest`` with some unique
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test execution modes:
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* Looponfail: run your tests repeatedly in a subprocess. After each
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run, ``pytest`` waits until a file in your project changes and then
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re-runs the previously failing tests. This is repeated until all
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tests pass. At this point a full run is again performed.
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* multiprocess Load-balancing: if you have multiple CPUs or hosts you can use
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them for a combined test run. This allows to speed up
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development or to use special resources of remote machines.
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* Multi-Platform coverage: you can specify different Python interpreters
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or different platforms and run tests in parallel on all of them.
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Before running tests remotely, ``pytest`` efficiently "rsyncs" your
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program source code to the remote place. All test results
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are reported back and displayed to your local terminal.
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You may specify different Python versions and interpreters.
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Installation of xdist plugin
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------------------------------
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Install the plugin with::
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easy_install pytest-xdist
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# or
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pip install pytest-xdist
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or use the package in develop/in-place mode with
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a checkout of the `pytest-xdist repository`_ ::
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python setup.py develop
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Usage examples
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---------------------
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.. _`xdistcpu`:
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Speed up test runs by sending tests to multiple CPUs
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+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
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To send tests to multiple CPUs, type::
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pytest -n NUM
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Especially for longer running tests or tests requiring
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a lot of I/O this can lead to considerable speed ups.
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Running tests in a Python subprocess
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+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
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To instantiate a Python-2.7 subprocess and send tests to it, you may type::
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pytest -d --tx popen//python=python2.7
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This will start a subprocess which is run with the "python2.7"
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Python interpreter, found in your system binary lookup path.
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If you prefix the --tx option value like this::
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pytest -d --tx 3*popen//python=python2.7
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then three subprocesses would be created and the tests
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will be distributed to three subprocesses and run simultanously.
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.. _looponfailing:
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Running tests in looponfailing mode
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+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
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For refactoring a project with a medium or large test suite
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you can use the looponfailing mode. Simply add the ``--f`` option::
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pytest -f
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and ``pytest`` will run your tests. Assuming you have failures it will then
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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
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can change it in your project by setting a configuration option::
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# content of a pytest.ini or tox.ini file
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[pytest]
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looponfailroots = mypkg testdir
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This would lead to only looking for file changes in the respective directories, specified relatively to the ini-file's directory.
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Sending tests to remote SSH accounts
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+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
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Suppose you have a package ``mypkg`` which contains some
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tests that you can successfully run locally. And you also
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have a ssh-reachable machine ``myhost``. Then
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you can ad-hoc distribute your tests by typing::
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pytest -d --tx ssh=myhostpopen --rsyncdir mypkg mypkg
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This will synchronize your ``mypkg`` package directory
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with a remote ssh account and then collect and run your
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tests at the remote side.
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You can specify multiple ``--rsyncdir`` directories
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to be sent to the remote side.
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.. XXX CHECK
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**NOTE:** For ``pytest`` to collect and send tests correctly
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you not only need to make sure all code and tests
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directories are rsynced, but that any test (sub) directory
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also has an ``__init__.py`` file because internally
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``pytest`` references tests as a fully qualified python
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module path. **You will otherwise get strange errors**
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during setup of the remote side.
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Sending tests to remote Socket Servers
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+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
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Download the single-module `socketserver.py`_ Python program
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and run it like this::
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python socketserver.py
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It will tell you that it starts listening on the default
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port. You can now on your home machine specify this
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new socket host with something like this::
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pytest -d --tx socket=192.168.1.102:8888 --rsyncdir mypkg mypkg
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.. _`atonce`:
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Running tests on many platforms at once
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+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
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The basic command to run tests on multiple platforms is::
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pytest --dist=each --tx=spec1 --tx=spec2
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If you specify a windows host, an OSX host and a Linux
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environment this command will send each tests to all
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platforms - and report back failures from all platforms
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at once. The specifications strings use the `xspec syntax`_.
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.. _`xspec syntax`: http://codespeak.net/execnet/basics.html#xspec
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.. _`socketserver.py`: http://bitbucket.org/hpk42/execnet/raw/2af991418160/execnet/script/socketserver.py
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.. _`execnet`: http://codespeak.net/execnet
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Specifying test exec environments in an ini file
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+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
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pytest (since version 2.0) supports ini-style configuration.
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For example, you could make running with three subprocesses your default::
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[pytest]
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addopts = -n3
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You can also add default environments like this::
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[pytest]
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addopts = --tx ssh=myhost//python=python2.7 --tx ssh=myhost//python=python2.6
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and then just type::
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pytest --dist=each
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to run tests in each of the environments.
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Specifying "rsync" dirs in an ini-file
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+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
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In a ``pytest.ini`` or ``tox.ini`` file in your root project directory
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you may specify directories to include or to exclude in synchronisation::
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[pytest]
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rsyncdirs = . mypkg helperpkg
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rsyncignore = .hg
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These directory specifications are relative to the directory
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where the configuration file was found.
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.. _`pytest-xdist`: http://pypi.python.org/pypi/pytest-xdist
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.. _`pytest-xdist repository`: http://bitbucket.org/pytest-dev/pytest-xdist
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.. _`pytest`: http://pytest.org
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