PYTEST-3(1) pytest PYTEST-3(1)
NAME
pytest - pytest usage
CALLING PYTEST-3 THROUGH PYTHON -M PYTEST-3
You can invoke testing through the Python interpreter from the command
line:
python -m pytest [...]
This is almost equivalent to invoking the command line script pytest
[...] directly, except that calling via python will also add the cur-
rent directory to sys.path.
POSSIBLE EXIT CODES
Running pytest can result in six different exit codes:
Exit code 0
All tests were collected and passed successfully
Exit code 1
Tests were collected and run but some of the tests failed
Exit code 2
Test execution was interrupted by the user
Exit code 3
Internal error happened while executing tests
Exit code 4
pytest command line usage error
Exit code 5
No tests were collected
They are represented by the pytest.ExitCode enum. The exit codes being
a part of the public API can be imported and accessed directly using:
from pytest import ExitCode
NOTE:
If you would like to customize the exit code in some scenarios, spe-
cially when no tests are collected, consider using the
pytest-custom_exit_code plugin.
GETTING HELP ON VERSION, OPTION NAMES, ENVIRONMENT VARIABLES
pytest --version # shows where pytest was imported from
pytest --fixtures # show available builtin function arguments
pytest -h | --help # show help on command line and config file options
The full command-line flags can be found in the reference.
STOPPING AFTER THE FIRST (OR N) FAILURES
To stop the testing process after the first (N) failures:
pytest -x # stop after first failure
pytest --maxfail=2 # stop after two failures
SPECIFYING TESTS / SELECTING TESTS
Pytest supports several ways to run and select tests from the com-
mand-line.
Run tests in a module
pytest test_mod.py
Run tests in a directory
pytest testing/
Run tests by keyword expressions
pytest -k "MyClass and not method"
This will run tests which contain names that match the given string ex-
pression (case-insensitive), which can include Python operators that
use filenames, class names and function names as variables. The exam-
ple above will run TestMyClass.test_something but not TestMy-
Class.test_method_simple.
Run tests by node ids
Each collected test is assigned a unique nodeid which consist of the
module filename followed by specifiers like class names, function names
and parameters from parametrization, separated by :: characters.
To run a specific test within a module:
pytest test_mod.py::test_func
Another example specifying a test method in the command line:
pytest test_mod.py::TestClass::test_method
Run tests by marker expressions
pytest -m slow
Will run all tests which are decorated with the @pytest.mark.slow deco-
rator.
For more information see marks.
Run tests from packages
pytest --pyargs pkg.testing
This will import pkg.testing and use its filesystem location to find
and run tests from.
MODIFYING PYTHON TRACEBACK PRINTING
Examples for modifying traceback printing:
pytest --showlocals # show local variables in tracebacks
pytest -l # show local variables (shortcut)
pytest --tb=auto # (default) 'long' tracebacks for the first and last
# entry, but 'short' style for the other entries
pytest --tb=long # exhaustive, informative traceback formatting
pytest --tb=short # shorter traceback format
pytest --tb=line # only one line per failure
pytest --tb=native # Python standard library formatting
pytest --tb=no # no traceback at all
The --full-trace causes very long traces to be printed on error (longer
than --tb=long). It also ensures that a stack trace is printed on Key-
boardInterrupt (Ctrl+C). This is very useful if the tests are taking
too long and you interrupt them with Ctrl+C to find out where the tests
are hanging. By default no output will be shown (because KeyboardInter-
rupt is caught by pytest). By using this option you make sure a trace
is shown.
DETAILED SUMMARY REPORT
The -r flag can be used to display a "short test summary info" at the
end of the test session, making it easy in large test suites to get a
clear picture of all failures, skips, xfails, etc.
It defaults to fE to list failures and errors.
Example:
# content of test_example.py
import pytest
@pytest.fixture
def error_fixture():
assert 0
def test_ok():
print("ok")
def test_fail():
assert 0
def test_error(error_fixture):
pass
def test_skip():
pytest.skip("skipping this test")
def test_xfail():
pytest.xfail("xfailing this test")
@pytest.mark.xfail(reason="always xfail")
def test_xpass():
pass
$ pytest -ra
=========================== test session starts ============================
platform linux -- Python 3.x.y, pytest-6.x.y, py-1.x.y, pluggy-1.x.y
cachedir: $PYTHON_PREFIX/.pytest_cache
rootdir: $REGENDOC_TMPDIR
collected 6 items
test_example.py .FEsxX [100%]
================================== ERRORS ==================================
_______________________ ERROR at setup of test_error _______________________
@pytest.fixture
def error_fixture():
> assert 0
E assert 0
test_example.py:6: AssertionError
================================= FAILURES =================================
________________________________ test_fail _________________________________
def test_fail():
> assert 0
E assert 0
test_example.py:14: AssertionError
========================= short test summary info ==========================
SKIPPED [1] test_example.py:22: skipping this test
XFAIL test_example.py::test_xfail
reason: xfailing this test
XPASS test_example.py::test_xpass always xfail
ERROR test_example.py::test_error - assert 0
FAILED test_example.py::test_fail - assert 0
== 1 failed, 1 passed, 1 skipped, 1 xfailed, 1 xpassed, 1 error in 0.12s ===
The -r options accepts a number of characters after it, with a used
above meaning "all except passes".
Here is the full list of available characters that can be used:
• f - failed
• E - error
• s - skipped
• x - xfailed
• X - xpassed
• p - passed
• P - passed with output
Special characters for (de)selection of groups:
• a - all except pP
• A - all
• N - none, this can be used to display nothing (since fE is the de-
fault)
More than one character can be used, so for example to only see failed
and skipped tests, you can execute:
$ pytest -rfs
=========================== test session starts ============================
platform linux -- Python 3.x.y, pytest-6.x.y, py-1.x.y, pluggy-1.x.y
cachedir: $PYTHON_PREFIX/.pytest_cache
rootdir: $REGENDOC_TMPDIR
collected 6 items
test_example.py .FEsxX [100%]
================================== ERRORS ==================================
_______________________ ERROR at setup of test_error _______________________
@pytest.fixture
def error_fixture():
> assert 0
E assert 0
test_example.py:6: AssertionError
================================= FAILURES =================================
________________________________ test_fail _________________________________
def test_fail():
> assert 0
E assert 0
test_example.py:14: AssertionError
========================= short test summary info ==========================
FAILED test_example.py::test_fail - assert 0
SKIPPED [1] test_example.py:22: skipping this test
== 1 failed, 1 passed, 1 skipped, 1 xfailed, 1 xpassed, 1 error in 0.12s ===
Using p lists the passing tests, whilst P adds an extra section
"PASSES" with those tests that passed but had captured output:
$ pytest -rpP
=========================== test session starts ============================
platform linux -- Python 3.x.y, pytest-6.x.y, py-1.x.y, pluggy-1.x.y
cachedir: $PYTHON_PREFIX/.pytest_cache
rootdir: $REGENDOC_TMPDIR
collected 6 items
test_example.py .FEsxX [100%]
================================== ERRORS ==================================
_______________________ ERROR at setup of test_error _______________________
@pytest.fixture
def error_fixture():
> assert 0
E assert 0
test_example.py:6: AssertionError
================================= FAILURES =================================
________________________________ test_fail _________________________________
def test_fail():
> assert 0
E assert 0
test_example.py:14: AssertionError
================================== PASSES ==================================
_________________________________ test_ok __________________________________
--------------------------- Captured stdout call ---------------------------
ok
========================= short test summary info ==========================
PASSED test_example.py::test_ok
== 1 failed, 1 passed, 1 skipped, 1 xfailed, 1 xpassed, 1 error in 0.12s ===
DROPPING TO PDB (PYTHON DEBUGGER) ON FAILURES
Python comes with a builtin Python debugger called PDB. pytest allows
one to drop into the PDB prompt via a command line option:
pytest --pdb
This will invoke the Python debugger on every failure (or Keyboard-
Interrupt). Often you might only want to do this for the first failing
test to understand a certain failure situation:
pytest -x --pdb # drop to PDB on first failure, then end test session
pytest --pdb --maxfail=3 # drop to PDB for first three failures
Note that on any failure the exception information is stored on
sys.last_value, sys.last_type and sys.last_traceback. In interactive
use, this allows one to drop into postmortem debugging with any debug
tool. One can also manually access the exception information, for exam-
ple:
>>> import sys
>>> sys.last_traceback.tb_lineno
42
>>> sys.last_value
AssertionError('assert result == "ok"',)
DROPPING TO PDB (PYTHON DEBUGGER) AT THE START OF A TEST
pytest allows one to drop into the PDB prompt immediately at the start
of each test via a command line option:
pytest --trace
This will invoke the Python debugger at the start of every test.
SETTING BREAKPOINTS
To set a breakpoint in your code use the native Python import
pdb;pdb.set_trace() call in your code and pytest automatically disables
its output capture for that test:
• Output capture in other tests is not affected.
• Any prior test output that has already been captured and will be pro-
cessed as such.
• Output capture gets resumed when ending the debugger session (via the
continue command).
USING THE BUILTIN BREAKPOINT FUNCTION
Python 3.7 introduces a builtin breakpoint() function. Pytest supports
the use of breakpoint() with the following behaviours:
• When breakpoint() is called and PYTHONBREAKPOINT is set to the de-
fault value, pytest will use the custom internal PDB trace UI in-
stead of the system default Pdb.
• When tests are complete, the system will default back to the sys-
tem Pdb trace UI.
• With --pdb passed to pytest, the custom internal Pdb trace UI is
used with both breakpoint() and failed tests/unhandled exceptions.
• --pdbcls can be used to specify a custom debugger class.
PROFILING TEST EXECUTION DURATION
Changed in version 6.0.
To get a list of the slowest 10 test durations over 1.0s long:
pytest --durations=10 --durations-min=1.0
By default, pytest will not show test durations that are too small
(<0.005s) unless -vv is passed on the command-line.
FAULT HANDLER
New in version 5.0.
The faulthandler standard module can be used to dump Python tracebacks
on a segfault or after a timeout.
The module is automatically enabled for pytest runs, unless the -p
no:faulthandler is given on the command-line.
Also the faulthandler_timeout=X configuration option can be used to
dump the traceback of all threads if a test takes longer than X seconds
to finish (not available on Windows).
NOTE:
This functionality has been integrated from the external
pytest-faulthandler plugin, with two small differences:
• To disable it, use -p no:faulthandler instead of --no-fault-
handler: the former can be used with any plugin, so it saves one
option.
• The --faulthandler-timeout command-line option has become the
faulthandler_timeout configuration option. It can still be config-
ured from the command-line using -o faulthandler_timeout=X.
WARNING ABOUT UNRAISABLE EXCEPTIONS AND UNHANDLED THREAD EXCEPTIONS
New in version 6.2.
NOTE:
These features only work on Python>=3.8.
Unhandled exceptions are exceptions that are raised in a situation in
which they cannot propagate to a caller. The most common case is an ex-
ception raised in a __del__ implementation.
Unhandled thread exceptions are exceptions raised in a Thread but not
handled, causing the thread to terminate uncleanly.
Both types of exceptions are normally considered bugs, but may go unno-
ticed because they don't cause the program itself to crash. Pytest de-
tects these conditions and issues a warning that is visible in the test
run summary.
The plugins are automatically enabled for pytest runs, unless the -p
no:unraisableexception (for unraisable exceptions) and -p no:threadex-
ception (for thread exceptions) options are given on the command-line.
The warnings may be silenced selectivly using the pytest.mark.filter-
warnings ref mark. The warning categories are pytest.PytestUnraisable-
ExceptionWarning and pytest.PytestUnhandledThreadExceptionWarning.
CREATING JUNITXML FORMAT FILES
To create result files which can be read by Jenkins or other Continuous
integration servers, use this invocation:
pytest --junitxml=path
to create an XML file at path.
To set the name of the root test suite xml item, you can configure the
junit_suite_name option in your config file:
[pytest]
junit_suite_name = my_suite
New in version 4.0.
JUnit XML specification seems to indicate that "time" attribute should
report total test execution times, including setup and teardown (1, 2).
It is the default pytest behavior. To report just call durations in-
stead, configure the junit_duration_report option like this:
[pytest]
junit_duration_report = call
record_property
If you want to log additional information for a test, you can use the
record_property fixture:
def test_function(record_property):
record_property("example_key", 1)
assert True
This will add an extra property example_key="1" to the generated test-
case tag:
<testcase classname="test_function" file="test_function.py" line="0" name="test_function" time="0.0009">
<properties>
<property name="example_key" value="1" />
</properties>
</testcase>
Alternatively, you can integrate this functionality with custom mark-
ers:
# content of conftest.py
def pytest_collection_modifyitems(session, config, items):
for item in items:
for marker in item.iter_markers(name="test_id"):
test_id = marker.args[0]
item.user_properties.append(("test_id", test_id))
And in your tests:
# content of test_function.py
import pytest
@pytest.mark.test_id(1501)
def test_function():
assert True
Will result in:
<testcase classname="test_function" file="test_function.py" line="0" name="test_function" time="0.0009">
<properties>
<property name="test_id" value="1501" />
</properties>
</testcase>
WARNING:
Please note that using this feature will break schema verifications
for the latest JUnitXML schema. This might be a problem when used
with some CI servers.
record_xml_attribute
To add an additional xml attribute to a testcase element, you can use
record_xml_attribute fixture. This can also be used to override exist-
ing values:
def test_function(record_xml_attribute):
record_xml_attribute("assertions", "REQ-1234")
record_xml_attribute("classname", "custom_classname")
print("hello world")
assert True
Unlike record_property, this will not add a new child element. In-
stead, this will add an attribute assertions="REQ-1234" inside the gen-
erated testcase tag and override the default classname with "class-
name=custom_classname":
<testcase classname="custom_classname" file="test_function.py" line="0" name="test_function" time="0.003" assertions="REQ-1234">
<system-out>
hello world
</system-out>
</testcase>
WARNING:
record_xml_attribute is an experimental feature, and its interface
might be replaced by something more powerful and general in future
versions. The functionality per-se will be kept, however.
Using this over record_xml_property can help when using ci tools to
parse the xml report. However, some parsers are quite strict about
the elements and attributes that are allowed. Many tools use an xsd
schema (like the example below) to validate incoming xml. Make sure
you are using attribute names that are allowed by your parser.
Below is the Scheme used by Jenkins to validate the XML report:
<xs:element name="testcase">
<xs:complexType>
<xs:sequence>
<xs:element ref="skipped" minOccurs="0" maxOccurs="1"/>
<xs:element ref="error" minOccurs="0" maxOccurs="unbounded"/>
<xs:element ref="failure" minOccurs="0" maxOccurs="unbounded"/>
<xs:element ref="system-out" minOccurs="0" maxOccurs="unbounded"/>
<xs:element ref="system-err" minOccurs="0" maxOccurs="unbounded"/>
</xs:sequence>
<xs:attribute name="name" type="xs:string" use="required"/>
<xs:attribute name="assertions" type="xs:string" use="optional"/>
<xs:attribute name="time" type="xs:string" use="optional"/>
<xs:attribute name="classname" type="xs:string" use="optional"/>
<xs:attribute name="status" type="xs:string" use="optional"/>
</xs:complexType>
</xs:element>
WARNING:
Please note that using this feature will break schema verifications
for the latest JUnitXML schema. This might be a problem when used
with some CI servers.
record_testsuite_property
New in version 4.5.
If you want to add a properties node at the test-suite level, which may
contains properties that are relevant to all tests, you can use the
record_testsuite_property session-scoped fixture:
The record_testsuite_property session-scoped fixture can be used to add
properties relevant to all tests.
import pytest
@pytest.fixture(scope="session", autouse=True)
def log_global_env_facts(record_testsuite_property):
record_testsuite_property("ARCH", "PPC")
record_testsuite_property("STORAGE_TYPE", "CEPH")
class TestMe:
def test_foo(self):
assert True
The fixture is a callable which receives name and value of a <property>
tag added at the test-suite level of the generated xml:
<testsuite errors="0" failures="0" name="pytest" skipped="0" tests="1" time="0.006">
<properties>
<property name="ARCH" value="PPC"/>
<property name="STORAGE_TYPE" value="CEPH"/>
</properties>
<testcase classname="test_me.TestMe" file="test_me.py" line="16" name="test_foo" time="0.000243663787842"/>
</testsuite>
name must be a string, value will be converted to a string and properly
xml-escaped.
The generated XML is compatible with the latest xunit standard, con-
trary to record_property and record_xml_attribute.
CREATING RESULTLOG FORMAT FILES
To create plain-text machine-readable result files you can issue:
pytest --resultlog=path
and look at the content at the path location. Such files are used e.g.
by the PyPy-test web page to show test results over several revisions.
WARNING:
This option is rarely used and is scheduled for removal in pytest
6.0.
If you use this option, consider using the new pytest-reportlog
plugin instead.
See the deprecation docs for more information.
SENDING TEST REPORT TO ONLINE PASTEBIN SERVICE
Creating a URL for each test failure:
pytest --pastebin=failed
This will submit test run information to a remote Paste service and
provide a URL for each failure. You may select tests as usual or add
for example -x if you only want to send one particular failure.
Creating a URL for a whole test session log:
pytest --pastebin=all
Currently only pasting to the http://bpaste.net service is implemented.
Changed in version 5.2.
If creating the URL fails for any reason, a warning is generated in-
stead of failing the entire test suite.
EARLY LOADING PLUGINS
You can early-load plugins (internal and external) explicitly in the
command-line with the -p option:
pytest -p mypluginmodule
The option receives a name parameter, which can be:
• A full module dotted name, for example myproject.plugins. This dotted
name must be importable.
• The entry-point name of a plugin. This is the name passed to setup-
tools when the plugin is registered. For example to early-load the
pytest-cov plugin you can use:
pytest -p pytest_cov
DISABLING PLUGINS
To disable loading specific plugins at invocation time, use the -p op-
tion together with the prefix no:.
Example: to disable loading the plugin doctest, which is responsible
for executing doctest tests from text files, invoke pytest like this:
pytest -p no:doctest
CALLING PYTEST-3 FROM PYTHON CODE
You can invoke pytest from Python code directly:
pytest.main()
this acts as if you would call "pytest" from the command line. It will
not raise SystemExit but return the exitcode instead. You can pass in
options and arguments:
pytest.main(["-x", "mytestdir"])
You can specify additional plugins to pytest.main:
# content of myinvoke.py
import pytest
class MyPlugin:
def pytest_sessionfinish(self):
print("*** test run reporting finishing")
pytest.main(["-qq"], plugins=[MyPlugin()])
Running it will show that MyPlugin was added and its hook was invoked:
$ python myinvoke.py
.FEsxX. [100%]*** test run reporting finishing
================================== ERRORS ==================================
_______________________ ERROR at setup of test_error _______________________
@pytest.fixture
def error_fixture():
> assert 0
E assert 0
test_example.py:6: AssertionError
================================= FAILURES =================================
________________________________ test_fail _________________________________
def test_fail():
> assert 0
E assert 0
test_example.py:14: AssertionError
========================= short test summary info ==========================
FAILED test_example.py::test_fail - assert 0
ERROR test_example.py::test_error - assert 0
NOTE:
Calling pytest.main() will result in importing your tests and any
modules that they import. Due to the caching mechanism of python's
import system, making subsequent calls to pytest.main() from the
same process will not reflect changes to those files between the
calls. For this reason, making multiple calls to pytest.main() from
the same process (in order to re-run tests, for example) is not rec-
ommended.
AUTHOR
holger krekel at merlinux eu
COPYRIGHT
2015–2020, holger krekel and pytest-dev team
6.2.5 Feb 09, 2022 PYTEST-3(1)
Generated by dwww version 1.14 on Wed Jan 22 13:43:43 CET 2025.