If you have test functions that cannot be run on certain platforms or that you expect to fail you can mark them accordingly or you may call helper functions during execution of setup or test functions.
A skip means that you expect your test to pass unless a certain configuration or condition (e.g. wrong Python interpreter, missing dependency) prevents it to run. And xfail means that your test can run but you expect it to fail because there is an implementation problem.
py.test counts and lists skip and xfail tests separately. However, detailed information about skipped/xfailed tests is not shown by default to avoid cluttering the output. You can use the -r option to see details corresponding to the “short” letters shown in the test progress:
py.test -rxs # show extra info on skips and xfails
Here is an example of marking a test function to be skipped when run on a Python3 interpreter:
import sys @pytest.mark.skipif("sys.version_info >= (3,0)") def test_function(): ...
During test function setup the skipif condition is evaluated by calling eval('sys.version_info >= (3,0)', namespace). (New in version 2.0.2) The namespace contains all the module globals of the test function so that you can for example check for versions of a module you are using:
import mymodule @pytest.mark.skipif("mymodule.__version__ < '1.2'") def test_function(): ...
The test function will not be run (“skipped”) if mymodule is below the specified version. The reason for specifying the condition as a string is mainly that py.test can report a summary of skip conditions. For information on the construction of the namespace see evaluation of skipif/xfail conditions.
You can of course create a shortcut for your conditional skip decorator at module level like this:
win32only = pytest.mark.skipif("sys.platform != 'win32'") @win32only def test_function(): ...
class TestPosixCalls: pytestmark = pytest.mark.skipif("sys.platform == 'win32'") def test_function(self): "will not be setup or run under 'win32' platform"
The pytestmark special name tells py.test to apply it to each test function in the class. If your code targets python2.6 or above you can more naturally use the skipif decorator (and any other marker) on classes:
@pytest.mark.skipif("sys.platform == 'win32'") class TestPosixCalls: def test_function(self): "will not be setup or run under 'win32' platform"
Using multiple “skipif” decorators on a single function is generally fine - it means that if any of the conditions apply the function execution will be skipped.
You can use the xfail marker to indicate that you expect the test to fail:
@pytest.mark.xfail def test_function(): ...
This test will be run but no traceback will be reported when it fails. Instead terminal reporting will list it in the “expected to fail” or “unexpectedly passing” sections.
By specifying on the commandline:
you can force the running and reporting of an xfail marked test as if it weren’t marked at all.
As with skipif you can also mark your expectation of a failure on a particular platform:
@pytest.mark.xfail("sys.version_info >= (3,0)") def test_function(): ...
You can furthermore prevent the running of an “xfail” test or specify a reason such as a bug ID or similar. Here is a simple test file with the several usages:
import pytest xfail = pytest.mark.xfail @xfail def test_hello(): assert 0 @xfail(run=False) def test_hello2(): assert 0 @xfail("hasattr(os, 'sep')") def test_hello3(): assert 0 @xfail(reason="bug 110") def test_hello4(): assert 0 @xfail('pytest.__version__ != "17"') def test_hello5(): assert 0 def test_hello6(): pytest.xfail("reason")
Running it with the report-on-xfail option gives this output:
example $ py.test -rx xfail_demo.py =========================== test session starts ============================ platform linux2 -- Python 2.7.3 -- pytest-2.3.5 collected 6 items xfail_demo.py xxxxxx ========================= short test summary info ========================== XFAIL xfail_demo.py::test_hello XFAIL xfail_demo.py::test_hello2 reason: [NOTRUN] XFAIL xfail_demo.py::test_hello3 condition: hasattr(os, 'sep') XFAIL xfail_demo.py::test_hello4 bug 110 XFAIL xfail_demo.py::test_hello5 condition: pytest.__version__ != "17" XFAIL xfail_demo.py::test_hello6 reason: reason ======================== 6 xfailed in 0.05 seconds =========================
New in version 2.0.2.
The evaluation of a condition string in pytest.mark.skipif(conditionstring) or pytest.mark.xfail(conditionstring) takes place in a namespace dictionary which is constructed as follows:
The pytest config object allows you to skip based on a test configuration value which you might have added:
@pytest.mark.skipif("not config.getvalue('db')") def test_function(...): ...
If you cannot declare xfail-conditions at import time you can also imperatively produce an XFail-outcome from within test or setup code. Example:
def test_function(): if not valid_config(): pytest.xfail("unsupported configuration")
You can use the following import helper at module level or within a test or test setup function:
docutils = pytest.importorskip("docutils")
If docutils cannot be imported here, this will lead to a skip outcome of the test. You can also skip based on the version number of a library:
docutils = pytest.importorskip("docutils", minversion="0.3")
The version will be read from the specified module’s __version__ attribute.
If for some reason you cannot declare skip-conditions you can also imperatively produce a skip-outcome from within test or setup code. Example:
def test_function(): if not valid_config(): pytest.skip("unsupported configuration")