Historical Notes

This page lists features or behavior from previous versions of pytest which have changed over the years. They are kept here as a historical note so users looking at old code can find documentation related to them.

cache plugin integrated into the core

New in version 2.8.

The functionality of the core cache plugin was previously distributed as a third party plugin named pytest-cache. The core plugin is compatible regarding command line options and API usage except that you can only store/receive data between test runs that is json-serializable.

funcargs and pytest_funcarg__

Changed in version 2.3.

In versions prior to 2.3 there was no @pytest.fixture marker and you had to use a magic pytest_funcarg__NAME prefix for the fixture factory. This remains and will remain supported but is not anymore advertised as the primary means of declaring fixture functions.

@pytest.yield_fixture decorator

Changed in version 2.10.

Prior to version 2.10, in order to use a yield statement to execute teardown code one had to mark a fixture using the yield_fixture marker. From 2.10 onward, normal fixtures can use yield directly so the yield_fixture decorator is no longer needed and considered deprecated.

[pytest] header in setup.cfg

Changed in version 3.0.

Prior to 3.0, the supported section name was [pytest]. Due to how this may collide with some distutils commands, the recommended section name for setup.cfg files is now [tool:pytest].

Note that for pytest.ini and tox.ini files the section name is [pytest].

Applying marks to @pytest.mark.parametrize parameters

Changed in version 3.1.

Prior to version 3.1 the supported mechanism for marking values used the syntax:

import pytest
@pytest.mark.parametrize("test_input,expected", [
    ("3+5", 8),
    ("2+4", 6),
    pytest.mark.xfail(("6*9", 42),),
])
def test_eval(test_input, expected):
    assert eval(test_input) == expected

This was an initial hack to support the feature but soon was demonstrated to be incomplete, broken for passing functions or applying multiple marks with the same name but different parameters.

The old syntax is planned to be removed in pytest-4.0.

@pytest.mark.parametrize argument names as a tuple

Changed in version 2.4.

In versions prior to 2.4 one needed to specify the argument names as a tuple. This remains valid but the simpler "name1,name2,..." comma-separated-string syntax is now advertised first because it’s easier to write and produces less line noise.

setup: is now an “autouse fixture”

Changed in version 2.3.

During development prior to the pytest-2.3 release the name pytest.setup was used but before the release it was renamed and moved to become part of the general fixture mechanism, namely Autouse fixtures (xUnit setup on steroids)

Conditions as strings instead of booleans

Changed in version 2.4.

Prior to pytest-2.4 the only way to specify skipif/xfail conditions was to use strings:

import sys
@pytest.mark.skipif("sys.version_info >= (3,3)")
def test_function():
    ...

During test function setup the skipif condition is evaluated by calling eval('sys.version_info >= (3,0)', namespace). The namespace contains all the module globals, and os and sys as a minimum.

Since pytest-2.4 boolean conditions are considered preferable because markers can then be freely imported between test modules. With strings you need to import not only the marker but all variables used by the marker, which violates encapsulation.

The reason for specifying the condition as a string was that pytest can report a summary of skip conditions based purely on the condition string. With conditions as booleans you are required to specify a reason string.

Note that string conditions will remain fully supported and you are free to use them if you have no need for cross-importing markers.

The evaluation of a condition string in pytest.mark.skipif(conditionstring) or pytest.mark.xfail(conditionstring) takes place in a namespace dictionary which is constructed as follows:

• the namespace is initialized by putting the sys and os modules and the pytest config object into it.
• updated with the module globals of the test function for which the expression is applied.

The pytest config object allows you to skip based on a test configuration value which you might have added:

@pytest.mark.skipif("not config.getvalue('db')")
def test_function(...):
    ...

The equivalent with “boolean conditions” is:

@pytest.mark.skipif(not pytest.config.getvalue("db"),
                    reason="--db was not specified")
def test_function(...):
    pass

Note

You cannot use pytest.config.getvalue() in code imported before pytest’s argument parsing takes place. For example, conftest.py files are imported before command line parsing and thus config.getvalue() will not execute correctly.

pytest.set_trace()

Changed in version 2.4.

Previous to version 2.4 to set a break point in code one needed to use pytest.set_trace():

import pytest
def test_function():
    ...
    pytest.set_trace()    # invoke PDB debugger and tracing

This is no longer needed and one can use the native import pdb;pdb.set_trace() call directly.

For more details see Setting breakpoints.