233 lines
7.8 KiB
Plaintext
233 lines
7.8 KiB
Plaintext
Installation and Getting Started
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===================================
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**Compatibility**: Python 2.4-3.2, Jython, PyPy on Unix/Posix and Windows
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Installation
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----------------------------------------
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Installation options::
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easy_install -U pytest # or
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pip install -U pytest
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To check your installation has installed the correct version::
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$ py.test --version
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This is py.test version 2.0.0.dev22, imported from /home/hpk/p/pytest/pytest
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If you get an error checkout :ref:`installation issues`.
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Our first test run
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----------------------------------------------------------
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Let's create a first test file with a simple test function::
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# content of test_sample.py
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def func(x):
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return x + 1
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def test_answer():
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assert func(3) == 5
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That's it. You can execute the test function now::
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$ py.test
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=========================== test session starts ============================
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platform linux2 -- Python 2.6.5 -- pytest-2.0.0.dev22
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test path 1: /tmp/doc-exec-523
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test_sample.py F
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================================= FAILURES =================================
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_______________________________ test_answer ________________________________
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def test_answer():
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> assert func(3) == 5
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E assert 4 == 5
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E + where 4 = func(3)
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test_sample.py:5: AssertionError
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========================= 1 failed in 0.02 seconds =========================
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py.test found the ``test_answer`` function by following :ref:`standard test discovery rules <test discovery>`, basically detecting the ``test_`` prefixes. We got a failure report because our little ``func(3)`` call did not return ``5``. The report is formatted using the :ref:`standard traceback reporting`.
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.. note::
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You can simply use the ``assert`` statement for coding expectations because
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intermediate values will be presented to you. This is much easier than
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learning all the `the JUnit legacy methods`_ which are even inconsistent
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with Python's own coding guidelines (but consistent with
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Java-style naming).
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There is only one seldomly hit caveat to using asserts: if your
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assertion expression fails and has side effects then re-evaluating
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it for presenting intermediate values can go wrong. It's easy to fix:
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compute the value ahead of the assert and then do the
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assertion or use the assert "message" syntax::
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assert expr, "message" # show "message" if expr is not True
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.. _`the JUnit legacy methods`: http://docs.python.org/library/unittest.html#test-cases
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.. _`assert statement`: http://docs.python.org/reference/simple_stmts.html#the-assert-statement
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Asserting a certain exception is raised
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--------------------------------------------------------------
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If you want to assert some code raises an exception you can
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use the ``raises`` helper::
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# content of test_sysexit.py
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import py
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def f():
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raise SystemExit(1)
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def test_mytest():
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with py.test.raises(SystemExit):
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f()
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Running it with, this time in "quiet" reporting mode::
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$ py.test -q test_sysexit.py
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.
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1 passed in 0.01 seconds
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.. todo:: For further ways to assert exceptions see the `raises`
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Grouping multiple tests in a class
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--------------------------------------------------------------
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If you start to have more than a few tests it often makes sense
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to group tests logically, in classes and modules. Let's put two
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tests in a class like this::
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# content of test_class.py
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class TestClass:
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def test_one(self):
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x = "this"
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assert 'h' in x
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def test_two(self):
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x = "hello"
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assert hasattr(x, 'check')
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The two tests are found because of the standard :ref:`test discovery`.
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There is no need to subclass anything. We can simply
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run the module by passing its filename::
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$ py.test -q test_class.py
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.F
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================================= FAILURES =================================
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____________________________ TestClass.test_two ____________________________
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self = <test_class.TestClass instance at 0x254f6c8>
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def test_two(self):
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x = "hello"
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> assert hasattr(x, 'check')
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E assert hasattr('hello', 'check')
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test_class.py:8: AssertionError
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1 failed, 1 passed in 0.03 seconds
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The first test passed, the second failed. Again we can easily see
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the intermediate values used in the assertion, helping us to
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understand the reason for the failure.
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Going functional: requesting a unique temporary directory
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--------------------------------------------------------------
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For functional tests one often needs to create some files
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and pass them to application objects. py.test provides
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the versatile :ref:`funcarg mechanism` which allows to request
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arbitrary resources, for example a unique temporary directory::
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# content of test_tmpdir.py
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def test_needsfiles(tmpdir):
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print tmpdir
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assert 0
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We list the name ``tmpdir`` in the test function signature and
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py.test will lookup and call a factory to create the resource
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before performing the test function call. Let's just run it::
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$ py.test -q test_tmpdir.py
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F
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================================= FAILURES =================================
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_____________________________ test_needsfiles ______________________________
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tmpdir = local('/tmp/pytest-446/test_needsfiles0')
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def test_needsfiles(tmpdir):
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print tmpdir
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> assert 0
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E assert 0
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test_tmpdir.py:3: AssertionError
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----------------------------- Captured stdout ------------------------------
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/tmp/pytest-446/test_needsfiles0
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1 failed in 0.07 seconds
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Before the test runs, a unique-per-test-invocation temporary directory
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was created. More info at :ref:`tmpdir handling`.
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You can find out what kind of builtin :ref:`funcargs` exist by typing::
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py.test --funcargs # shows builtin and custom function arguments
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where to go next
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-------------------------------------
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Here are a few suggestions where to go next:
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* :ref:`cmdline` for command line invocation examples
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* :ref:`good practises` for virtualenv, test layout, genscript support
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* :ref:`apiref` for documentation and examples on using py.test
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* :ref:`plugins` managing and writing plugins
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.. _`installation issues`:
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Known Installation issues
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------------------------------
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easy_install or pip not found?
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++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
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Consult `distribute docs <distribute>`_ to install the ``easy_install``
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tool on your machine. You may also use the original but somewhat older
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`setuptools`_ project although we generally recommend to use
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``distribute`` because it contains more bug fixes and also works for
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Python3.
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For Python2 you can also consult pip_ for the popular ``pip`` tool.
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However, If you want to install on Python3 you need to use Distribute_ which
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provides the ``easy_install`` utility.
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py.test not found on Windows despite installation?
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++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
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.. _`Python for Windows`: http://www.imladris.com/Scripts/PythonForWindows.html
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- **Windows**: If "easy_install" or "py.test" are not found
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please see here for preparing your environment for running
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command line tools: `Python for Windows`_. You may alternatively
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use an `ActivePython install`_ which makes command line tools
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automatically available under Windows.
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.. _`ActivePython install`: http://www.activestate.com/activepython/downloads
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.. _`Jython does not create command line launchers`: http://bugs.jython.org/issue1491
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- **Jython2.5.1 on Windows XP**: `Jython does not create command line launchers`_
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so ``py.test`` will not work correctly. You may install py.test on
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CPython and type ``py.test --genscript=mytest`` and then use
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``jython mytest`` to run py.test for your tests to run in Jython.
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:ref:`examples` for more complex examples
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.. include:: links.inc
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