How to use skip and xfail to deal with tests that cannot succeed¶
You can mark test functions that cannot be run on certain platforms or that you expect to fail so pytest can deal with them accordingly and present a summary of the test session, while keeping the test suite green.
A skip means that you expect your test to pass only if some conditions are met, otherwise pytest should skip running the test altogether. Common examples are skipping windows-only tests on non-windows platforms, or skipping tests that depend on an external resource which is not available at the moment (for example a database).
An xfail means that you expect a test to fail for some reason.
A common example is a test for a feature not yet implemented, or a bug not yet fixed.
When a test passes despite being expected to fail (marked with
it’s an xpass and will be reported in the test summary.
pytest counts and lists skip and xfail tests separately. 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:
pytest -rxXs # show extra info on xfailed, xpassed, and skipped tests
More details on the
-r option can be found by running
Skipping test functions¶
The simplest way to skip a test function is to mark it with the
which may be passed an optional
@pytest.mark.skip(reason="no way of currently testing this") def test_the_unknown(): ...
Alternatively, it is also possible to skip imperatively during test execution or setup
by calling the
def test_function(): if not valid_config(): pytest.skip("unsupported configuration")
The imperative method is useful when it is not possible to evaluate the skip condition during import time.
It is also possible to skip the whole module using
pytest.skip(reason, allow_module_level=True) at the module level:
import sys import pytest if not sys.platform.startswith("win"): pytest.skip("skipping windows-only tests", allow_module_level=True)
If you wish to skip something conditionally then you can use
Here is an example of marking a test function to be skipped
when run on an interpreter earlier than Python3.6:
import sys @pytest.mark.skipif(sys.version_info < (3, 7), reason="requires python3.7 or higher") def test_function(): ...
If the condition evaluates to
True during collection, the test function will be skipped,
with the specified reason appearing in the summary when using
You can share
skipif markers between modules. Consider this test module:
# content of test_mymodule.py import mymodule minversion = pytest.mark.skipif( mymodule.__versioninfo__ < (1, 1), reason="at least mymodule-1.1 required" ) @minversion def test_function(): ...
You can import the marker and reuse it in another test module:
# test_myothermodule.py from test_mymodule import minversion @minversion def test_anotherfunction(): ...
For larger test suites it’s usually a good idea to have one file where you define the markers which you then consistently apply throughout your test suite.
Alternatively, you can use condition strings instead of booleans, but they can’t be shared between modules easily so they are supported mainly for backward compatibility reasons.
Skip all test functions of a class or module¶
You can use the
skipif marker (as any other marker) on classes:
@pytest.mark.skipif(sys.platform == "win32", reason="does not run on windows") class TestPosixCalls: def test_function(self): "will not be setup or run under 'win32' platform"
If the condition is
True, this marker will produce a skip result for
each of the test methods of that class.
If you want to skip all test functions of a module, you may use the
# test_module.py pytestmark = pytest.mark.skipif(...)
skipif decorators are applied to a test function, it
will be skipped if any of the skip conditions is true.
Skipping files or directories¶
Sometimes you may need to skip an entire file or directory, for example if the tests rely on Python version-specific features or contain code that you do not wish pytest to run. In this case, you must exclude the files and directories from collection. Refer to Customizing test collection for more information.
Skipping on a missing import dependency¶
You can skip tests on a missing import by using pytest.importorskip at module level, within a test, or test setup function.
docutils = pytest.importorskip("docutils")
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
Here’s a quick guide on how to skip tests in a module in different situations:
Skip all tests in a module unconditionally:
pytestmark = pytest.mark.skip("all tests still WIP")
Skip all tests in a module based on some condition:
pytestmark = pytest.mark.skipif(sys.platform == "win32", reason="tests for linux only")
Skip all tests in a module if some import is missing:
pexpect = pytest.importorskip("pexpect")
XFail: mark test functions as expected to fail¶
You can use the
xfail marker to indicate that you
expect a test to fail:
@pytest.mark.xfail def test_function(): ...
This test will run but no traceback will be reported when it fails. Instead, terminal
reporting will list it in the “expected to fail” (
XFAIL) or “unexpectedly
Alternatively, you can also mark a test as
XFAIL from within the test or its setup function
def test_function(): if not valid_config(): pytest.xfail("failing configuration (but should work)")
def test_function2(): import slow_module if slow_module.slow_function(): pytest.xfail("slow_module taking too long")
These two examples illustrate situations where you don’t want to check for a condition at the module level, which is when a condition would otherwise be evaluated for marks.
This will make
XFAIL. Note that no other code is executed after
pytest.xfail() call, differently from the marker. That’s because it is implemented
internally by raising a known exception.
If a test is only expected to fail under a certain condition, you can pass that condition as the first parameter:
@pytest.mark.xfail(sys.platform == "win32", reason="bug in a 3rd party library") def test_function(): ...
Note that you have to pass a reason as well (see the parameter description at pytest.mark.xfail).
You can specify the motive of an expected failure with the
@pytest.mark.xfail(reason="known parser issue") def test_function(): ...
If you want to be more specific as to why the test is failing, you can specify
a single exception, or a tuple of exceptions, in the
@pytest.mark.xfail(raises=RuntimeError) def test_function(): ...
Then the test will be reported as a regular failure if it fails with an
exception not mentioned in
If a test should be marked as xfail and reported as such but should not be
even executed, use the
run parameter as
@pytest.mark.xfail(run=False) def test_function(): ...
This is specially useful for xfailing tests that are crashing the interpreter and should be investigated later.
XPASS don’t fail the test suite by default.
You can change this by setting the
strict keyword-only parameter to
@pytest.mark.xfail(strict=True) def test_function(): ...
This will make
XPASS (“unexpectedly passing”) results from this test to fail the test suite.
You can change the default value of the
strict parameter using the
xfail_strict ini option:
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. This also causes
pytest.xfail() to produce no effect.
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") @xfail(raises=IndexError) def test_hello7(): x =  x = 1
Running it with the report-on-xfail option gives this output:
example $ pytest -rx xfail_demo.py =========================== test session starts ============================ platform linux -- Python 3.x.y, pytest-6.x.y, py-1.x.y, pluggy-0.x.y cachedir: $PYTHON_PREFIX/.pytest_cache rootdir: $REGENDOC_TMPDIR/example collected 7 items xfail_demo.py xxxxxxx [100%] ========================= 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 XFAIL xfail_demo.py::test_hello7 ============================ 7 xfailed in 0.12s ============================
Skip/xfail with parametrize¶
It is possible to apply markers like skip and xfail to individual test instances when using parametrize:
import sys import pytest @pytest.mark.parametrize( ("n", "expected"), [ (1, 2), pytest.param(1, 0, marks=pytest.mark.xfail), pytest.param(1, 3, marks=pytest.mark.xfail(reason="some bug")), (2, 3), (3, 4), (4, 5), pytest.param( 10, 11, marks=pytest.mark.skipif(sys.version_info >= (3, 0), reason="py2k") ), ], ) def test_increment(n, expected): assert n + 1 == expected