Usage and Invocations¶
Calling pytest through
python -m pytest¶
New in version 2.0.
You can invoke testing through the Python interpreter from the command line:
python -m pytest [...]
This is equivalent to invoking the command line script
Getting help on version, option names, environment variables¶
py.test --version # shows where pytest was imported from py.test --fixtures # show available builtin function arguments py.test -h | --help # show help on command line and config file options
Stopping after the first (or N) failures¶
To stop the testing process after the first (N) failures:
py.test -x # stop after first failure py.test --maxfail=2 # stop after two failures
Specifying tests / selecting tests¶
Several test run options:
py.test test_mod.py # run tests in module py.test somepath # run all tests below somepath py.test -k stringexpr # only run tests with names that match the # "string expression", e.g. "MyClass and not method" # will select TestMyClass.test_something # but not TestMyClass.test_method_simple py.test test_mod.py::test_func # only run tests that match the "node ID", # e.g "test_mod.py::test_func" will select # only test_func in test_mod.py py.test test_mod.py::TestClass::test_method # run a single method in # a single class
Import ‘pkg’ and use its filesystem location to find and run tests:
py.test --pyargs pkg # run all tests found below directory of pypkg
Modifying Python traceback printing¶
Examples for modifying traceback printing:
py.test --showlocals # show local variables in tracebacks py.test -l # show local variables (shortcut) py.test --tb=auto # (default) 'long' tracebacks for the first and last # entry, but 'short' style for the other entries py.test --tb=long # exhaustive, informative traceback formatting py.test --tb=short # shorter traceback format py.test --tb=line # only one line per failure py.test --tb=native # Python standard library formatting py.test --tb=no # no traceback at all
This will invoke the Python debugger on every failure. Often you might only want to do this for the first failing test to understand a certain failure situation:
py.test -x --pdb # drop to PDB on first failure, then end test session py.test --pdb --maxfail=3 # drop to PDB for first three failures
Note that on any failure the exception information is stored on
interactive use, this allows one to drop into postmortem debugging with
any debug tool. One can also manually access the exception information,
>>> import sys >>> sys.last_traceback.tb_lineno 42 >>> sys.last_value AssertionError('assert result == "ok"',)
Setting a breakpoint / aka
If you want to set a breakpoint and enter the
can use a helper:
import pytest def test_function(): ... pytest.set_trace() # invoke PDB debugger and tracing
Prior to pytest version 2.0.0 you could only enter PDB tracing if you disabled
capturing on the command line via
py.test -s. In later versions, pytest
automatically disables its output capture when you enter PDB tracing:
- Output capture in other tests is not affected.
- Any prior test output that has already been captured and will be processed as such.
- Any later output produced within the same test will not be captured and will
instead get sent directly to
sys.stdout. Note that this holds true even for test output occurring after you exit the interactive PDB tracing session and continue with the regular test run.
Since pytest version 2.4.0 you can also use the native Python
import pdb;pdb.set_trace() call to enter PDB tracing without having to use
pytest.set_trace() wrapper or explicitly disable pytest’s output
Profiling test execution duration¶
To get a list of the slowest 10 test durations:
Creating JUnitXML format files¶
To create result files which can be read by Hudson or other Continuous integration servers, use this invocation:
to create an XML file at
New in version 2.8.
If you want to log additional information for a test, you can use the
def test_function(record_xml_property): record_xml_property("example_key", 1) assert 0
This will add an extra property
example_key="1" to the generated
<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>
This 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.
Currently it does not work when used with the
Also please note that using this feature will break any schema verification. This might be a problem when used with some CI servers.
Creating resultlog format files¶
To create plain-text machine-readable result files you can issue:
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.
Sending test report to online pastebin service¶
Creating a URL for each test failure:
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
-x if you only want to send one particular failure.
Creating a URL for a whole test session log:
Currently only pasting to the http://bpaste.net service is implemented.
To disable loading specific plugins at invocation time, use the
together with the prefix
Example: to disable loading the plugin
doctest, which is responsible for
executing doctest tests from text files, invoke py.test like this:
py.test -p no:doctest
Calling pytest from Python code¶
New in version 2.0.
You can invoke
pytest from Python code directly:
this acts as if you would call “py.test” from the command line.
It will not raise
SystemExit but return the exitcode instead.
You can pass in options and arguments:
or pass in a string:
You can specify additional plugins to
# 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 *** test run reporting finishing