How to invoke pytest

In general, pytest is invoked with the command pytest (see below for other ways to invoke pytest). This will execute all tests in all files whose names follow the form test_*.py or \* in the current directory and its subdirectories. More generally, pytest follows standard test discovery rules.

Specifying which tests to run

Pytest supports several ways to run and select tests from the command-line.

Run tests in a module


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 expression (case-insensitive), which can include Python operators that use filenames, class names and function names as variables. The example above will run TestMyClass.test_something but not TestMyClass.test_method_simple. Use "" instead of '' in expression when running this on Windows

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:


Another example specifying a test method in the command line:


Run tests by marker expressions

pytest -m slow

Will run all tests which are decorated with the @pytest.mark.slow decorator.

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.

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

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.

Managing loading of plugins

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 setuptools 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 option 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

Other ways of calling pytest

Calling pytest through python -m pytest

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 current directory to sys.path.

Calling pytest from Python code

You can invoke pytest from Python code directly:

retcode = pytest.main()

this acts as if you would call “pytest” from the command line. It will not raise SystemExit but return the exit code instead. If you don’t pass it any arguments, main reads the arguments from the command line arguments of the process (sys.argv), which may be undesirable. You can pass in options and arguments explicitly:

retcode = pytest.main(["-x", "mytestdir"])

You can specify additional plugins to pytest.main:

# content of
import sys

import pytest

class MyPlugin:
    def pytest_sessionfinish(self):
        print("*** test run reporting finishing")

if __name__ == "__main__":
    sys.exit(pytest.main(["-qq"], plugins=[MyPlugin()]))

Running it will show that MyPlugin was added and its hook was invoked:

$ python
*** test run reporting finishing


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 recommended.