199 lines
9.9 KiB
Plaintext
199 lines
9.9 KiB
Plaintext
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.. highlightlang:: python
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.. _myapp:
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Building an SSH connecting Application fixture
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==========================================================
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The goal of this tutorial-example is to show how you can put efficient
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test support and fixture code in one place, allowing test modules and
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test functions to stay ignorant of importing, configuration or
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setup/teardown details.
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The tutorial implements a simple ``RemoteInterpreter`` object that
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allows evaluation of python expressions. We are going to use
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the `execnet <http://codespeak.net/execnet>`_ package for the
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underlying cross-python bridge functionality.
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Step 1: Implementing a first test
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--------------------------------------------------------------
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Let's write a simple test function using a not yet defined ``interp`` fixture::
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# content of test_remoteinterpreter.py
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def test_eval_simple(interp):
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assert interp.eval("6*9") == 42
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The test function needs an argument named `interp` and therefore pytest will
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look for a :ref:`fixture function` that matches this name. We'll define it
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in a :ref:`local plugin <localplugin>` to make it available also to other
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test modules::
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# content of conftest.py
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from .remoteinterpreter import RemoteInterpreter
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@pytest.fixture
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def interp(request):
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import execnet
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gw = execnet.makegateway()
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return RemoteInterpreter(gw)
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To run the example we furthermore need to implement a RemoteInterpreter
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object which working with the injected execnet-gateway connection::
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# content of remoteintepreter.py
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class RemoteInterpreter:
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def __init__(self, gateway):
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self.gateway = gateway
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def eval(self, expression):
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# execnet open a "gateway" to the remote process
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# which enables to remotely execute code and communicate
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# to and fro via channels
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ch = self.gateway.remote_exec("channel.send(%s)" % expression)
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return ch.receive()
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That's it, we can now run the test::
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$ py.test test_remoteinterpreter.py
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Traceback (most recent call last):
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File "/home/hpk/p/pytest/.tox/regen/bin/py.test", line 9, in <module>
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load_entry_point('pytest==2.3.0', 'console_scripts', 'py.test')()
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File "/home/hpk/p/pytest/.tox/regen/local/lib/python2.7/site-packages/_pytest/core.py", line 473, in main
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config = _prepareconfig(args, plugins)
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File "/home/hpk/p/pytest/.tox/regen/local/lib/python2.7/site-packages/_pytest/core.py", line 463, in _prepareconfig
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pluginmanager=_pluginmanager, args=args)
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File "/home/hpk/p/pytest/.tox/regen/local/lib/python2.7/site-packages/_pytest/core.py", line 422, in __call__
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return self._docall(methods, kwargs)
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File "/home/hpk/p/pytest/.tox/regen/local/lib/python2.7/site-packages/_pytest/core.py", line 433, in _docall
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res = mc.execute()
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File "/home/hpk/p/pytest/.tox/regen/local/lib/python2.7/site-packages/_pytest/core.py", line 351, in execute
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res = method(**kwargs)
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File "/home/hpk/p/pytest/.tox/regen/local/lib/python2.7/site-packages/_pytest/helpconfig.py", line 25, in pytest_cmdline_parse
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config = __multicall__.execute()
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File "/home/hpk/p/pytest/.tox/regen/local/lib/python2.7/site-packages/_pytest/core.py", line 351, in execute
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res = method(**kwargs)
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File "/home/hpk/p/pytest/.tox/regen/local/lib/python2.7/site-packages/_pytest/config.py", line 10, in pytest_cmdline_parse
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config.parse(args)
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File "/home/hpk/p/pytest/.tox/regen/local/lib/python2.7/site-packages/_pytest/config.py", line 344, in parse
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self._preparse(args)
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File "/home/hpk/p/pytest/.tox/regen/local/lib/python2.7/site-packages/_pytest/config.py", line 322, in _preparse
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self._setinitialconftest(args)
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File "/home/hpk/p/pytest/.tox/regen/local/lib/python2.7/site-packages/_pytest/config.py", line 301, in _setinitialconftest
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self._conftest.setinitial(args)
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File "/home/hpk/p/pytest/.tox/regen/local/lib/python2.7/site-packages/_pytest/config.py", line 160, in setinitial
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self._try_load_conftest(anchor)
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File "/home/hpk/p/pytest/.tox/regen/local/lib/python2.7/site-packages/_pytest/config.py", line 166, in _try_load_conftest
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self._path2confmods[None] = self.getconftestmodules(anchor)
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File "/home/hpk/p/pytest/.tox/regen/local/lib/python2.7/site-packages/_pytest/config.py", line 190, in getconftestmodules
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clist[:0] = self.getconftestmodules(dp)
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File "/home/hpk/p/pytest/.tox/regen/local/lib/python2.7/site-packages/_pytest/config.py", line 189, in getconftestmodules
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clist.append(self.importconftest(conftestpath))
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File "/home/hpk/p/pytest/.tox/regen/local/lib/python2.7/site-packages/_pytest/config.py", line 218, in importconftest
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self._conftestpath2mod[conftestpath] = mod = conftestpath.pyimport()
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File "/home/hpk/p/pytest/.tox/regen/local/lib/python2.7/site-packages/py/_path/local.py", line 532, in pyimport
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__import__(modname)
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File "/tmp/doc-exec-286/conftest.py", line 2, in <module>
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from .remoteinterpreter import RemoteInterpreter
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ValueError: Attempted relative import in non-package
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.. _`tut-cmdlineoption`:
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Step 2: Adding command line configuration
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-----------------------------------------------------------
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To add a command line option we update the ``conftest.py`` of
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the previous example and add a command line option which
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is passed on to the MyApp object::
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# content of ./conftest.py
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import pytest
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from myapp import MyApp
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def pytest_addoption(parser): # pytest hook called during initialisation
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parser.addoption("--ssh", action="store", default=None,
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help="specify ssh host to run tests with")
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@pytest.fixture
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def mysetup(request): # "mysetup" factory function
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return MySetup(request.config)
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class MySetup:
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def __init__(self, config):
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self.config = config
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self.app = MyApp()
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def getsshconnection(self):
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import execnet
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host = self.config.option.ssh
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if host is None:
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pytest.skip("specify ssh host with --ssh")
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return execnet.SshGateway(host)
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Now any test function can use the ``mysetup.getsshconnection()`` method
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like this::
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# content of test_ssh.py
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class TestClass:
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def test_function(self, mysetup):
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conn = mysetup.getsshconnection()
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# work with conn
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Running it yields::
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$ py.test -q test_ssh.py -rs
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Traceback (most recent call last):
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File "/home/hpk/p/pytest/.tox/regen/bin/py.test", line 9, in <module>
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load_entry_point('pytest==2.3.0', 'console_scripts', 'py.test')()
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File "/home/hpk/p/pytest/.tox/regen/local/lib/python2.7/site-packages/_pytest/core.py", line 473, in main
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config = _prepareconfig(args, plugins)
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File "/home/hpk/p/pytest/.tox/regen/local/lib/python2.7/site-packages/_pytest/core.py", line 463, in _prepareconfig
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pluginmanager=_pluginmanager, args=args)
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File "/home/hpk/p/pytest/.tox/regen/local/lib/python2.7/site-packages/_pytest/core.py", line 422, in __call__
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return self._docall(methods, kwargs)
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File "/home/hpk/p/pytest/.tox/regen/local/lib/python2.7/site-packages/_pytest/core.py", line 433, in _docall
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res = mc.execute()
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File "/home/hpk/p/pytest/.tox/regen/local/lib/python2.7/site-packages/_pytest/core.py", line 351, in execute
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res = method(**kwargs)
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File "/home/hpk/p/pytest/.tox/regen/local/lib/python2.7/site-packages/_pytest/helpconfig.py", line 25, in pytest_cmdline_parse
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config = __multicall__.execute()
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File "/home/hpk/p/pytest/.tox/regen/local/lib/python2.7/site-packages/_pytest/core.py", line 351, in execute
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res = method(**kwargs)
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File "/home/hpk/p/pytest/.tox/regen/local/lib/python2.7/site-packages/_pytest/config.py", line 10, in pytest_cmdline_parse
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config.parse(args)
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File "/home/hpk/p/pytest/.tox/regen/local/lib/python2.7/site-packages/_pytest/config.py", line 344, in parse
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self._preparse(args)
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File "/home/hpk/p/pytest/.tox/regen/local/lib/python2.7/site-packages/_pytest/config.py", line 322, in _preparse
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self._setinitialconftest(args)
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File "/home/hpk/p/pytest/.tox/regen/local/lib/python2.7/site-packages/_pytest/config.py", line 301, in _setinitialconftest
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self._conftest.setinitial(args)
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File "/home/hpk/p/pytest/.tox/regen/local/lib/python2.7/site-packages/_pytest/config.py", line 160, in setinitial
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self._try_load_conftest(anchor)
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File "/home/hpk/p/pytest/.tox/regen/local/lib/python2.7/site-packages/_pytest/config.py", line 166, in _try_load_conftest
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self._path2confmods[None] = self.getconftestmodules(anchor)
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File "/home/hpk/p/pytest/.tox/regen/local/lib/python2.7/site-packages/_pytest/config.py", line 190, in getconftestmodules
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clist[:0] = self.getconftestmodules(dp)
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File "/home/hpk/p/pytest/.tox/regen/local/lib/python2.7/site-packages/_pytest/config.py", line 189, in getconftestmodules
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clist.append(self.importconftest(conftestpath))
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File "/home/hpk/p/pytest/.tox/regen/local/lib/python2.7/site-packages/_pytest/config.py", line 218, in importconftest
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self._conftestpath2mod[conftestpath] = mod = conftestpath.pyimport()
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File "/home/hpk/p/pytest/.tox/regen/local/lib/python2.7/site-packages/py/_path/local.py", line 532, in pyimport
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__import__(modname)
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File "/tmp/doc-exec-286/conftest.py", line 2, in <module>
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from myapp import MyApp
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ImportError: No module named myapp
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If you specify a command line option like ``py.test --ssh=python.org`` the test will execute as expected.
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Note that neither the ``TestClass`` nor the ``test_function`` need to
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know anything about how to setup the test state. It is handled separately
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in the ``conftest.py`` file. It is easy
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to extend the ``mysetup`` object for further needs in the test code - and for use by any other test functions in the files and directories below the ``conftest.py`` file.
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