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 pytest.mark.xfail), 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 pytest -h.
(See how to change command line options defaults{.interpreted-text
role=“ref”})
Skipping test functions{#skip}{#skipif} {#condition booleans}
The simplest way to skip a test function is to mark it with the skip
decorator which may be passed an optional reason:
@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 pytest.skip(reason) function:
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)
Reference: pytest.mark.skip ref{.interpreted-text role=“ref”}
skipif
If you wish to skip something conditionally then you can use skipif
instead. 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 -rs.
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 <string conditions>{.interpreted-text role=“ref”} instead of booleans,
but they can’t be shared between modules easily so they are supported
mainly for backward compatibility reasons.
Reference: pytest.mark.skipif ref{.interpreted-text role=“ref”}
Skip all test functions of a class or module
You can use the skipif marker (as any other marker) on classes:
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
pytestmark{.interpreted-text role=“globalvar”} global:
# test_module.py
pytestmark = pytest.mark.skipif(...)
If multiple 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{.interpreted-text role=“ref”} for more
information.
Skipping on a missing import dependency
You can skip tests on a missing import by using
pytest.importorskip ref{.interpreted-text role=“ref”} at module level,
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.
Summary
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:
- Skip all tests in a module if some import is missing:
pexpect = pytest.importorskip("pexpect")
XFail: mark test functions as expected to fail {#xfail}
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 passing” (XPASS) sections.
Alternatively, you can also mark a test as XFAIL from within the test
or its setup function imperatively:
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 test_function XFAIL. Note that no other code is
executed after the pytest.xfail{.interpreted-text role=“func”} call,
differently from the marker. That’s because it is implemented
internally by raising a known exception.
Reference: pytest.mark.xfail ref{.interpreted-text role=“ref”}
condition parameter
If a test is only expected to fail under a certain condition, you can
pass that condition as the first parameter:
def test_function():
...
Note that you have to pass a reason as well (see the parameter
description at pytest.mark.xfail ref{.interpreted-text role=“ref”}).
reason parameter
You can specify the motive of an expected failure with the reason
parameter:
@pytest.mark.xfail(reason="known parser issue")
def test_function():
...
raises parameter
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 raises
argument.
@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 raises.
run parameter
If a test should be marked as xfail and reported as such but should not
be even executed, use the run parameter as False:
@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.
strict parameter {#xfail strict tutorial}
Both XFAIL and XPASS don’t fail the test suite by default. You can
change this by setting the strict keyword-only parameter to True:
@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:
[pytest]
xfail_strict=true
Ignoring xfail
By specifying on the commandline:
pytest --runxfail
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{.interpreted-text role=“func”} to produce no effect.
Examples
Here is a simple test file with the several usages:
::: {.literalinclude}
example/xfail_demo.py
:::
Running it with the report-on-xfail option gives this output:
example $ pytest -rx xfail_demo.py
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%]
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__[0] != "17"
XFAIL xfail_demo.py::test_hello6
reason: reason
XFAIL xfail_demo.py::test_hello7
Skip/xfail with parametrize {#skip/xfail with parametrize}
It is possible to apply markers like skip and xfail to individual test
instances when using parametrize:
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):