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.

Marker revamp and iteration

Changed in version 3.6.

pytest’s marker implementation traditionally worked by simply updating the __dict__ attribute of functions to cumulatively add markers. As a result, markers would unintentionally be passed along class hierarchies in surprising ways. Further, the API for retrieving them was inconsistent, as markers from parameterization would be stored differently than markers applied using the @pytest.mark decorator and markers added via node.add_marker.

This state of things made it technically next to impossible to use data from markers correctly without having a deep understanding of the internals, leading to subtle and hard to understand bugs in more advanced usages.

Depending on how a marker got declared/changed one would get either a MarkerInfo which might contain markers from sibling classes, MarkDecorators when marks came from parameterization or from a node.add_marker call, discarding prior marks. Also MarkerInfo acts like a single mark, when it in fact represents a merged view on multiple marks with the same name.

On top of that markers were not accessible in the same way for modules, classes, and functions/methods. In fact, markers were only accessible in functions, even if they were declared on classes/modules.

A new API to access markers has been introduced in pytest 3.6 in order to solve the problems with the initial design, providing the _pytest.nodes.Node.iter_markers() method to iterate over markers in a consistent manner and reworking the internals, which solved a great deal of problems with the initial design.

Updating code

The old Node.get_marker(name) function is considered deprecated because it returns an internal MarkerInfo object which contains the merged name, *args and **kwargs of all the markers which apply to that node.

In general there are two scenarios on how markers should be handled:

1. Marks overwrite each other. Order matters but you only want to think of your mark as a single item. E.g. log_level('info') at a module level can be overwritten by log_level('debug') for a specific test.

In this case, use Node.get_closest_marker(name):

# replace this:
marker = item.get_marker("log_level")
if marker:
    level = marker.args[0]

# by this:
marker = item.get_closest_marker("log_level")
if marker:
    level = marker.args[0]

2. Marks compose in an additive manner. E.g. skipif(condition) marks mean you just want to evaluate all of them, order doesn’t even matter. You probably want to think of your marks as a set here.

In this case iterate over each mark and handle their *args and **kwargs individually.

# replace this
skipif = item.get_marker("skipif")
if skipif:
    for condition in skipif.args:
        # eval condition
        ...

# by this:
for skipif in item.iter_markers("skipif"):
    condition = skipif.args[0]
    # eval condition

If you are unsure or have any questions, please consider opening an issue.

cache plugin integrated into the core

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__

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

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

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

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

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”

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 自动使用的 fixtures（不需要显式请求的 fixtures）

Conditions as strings instead of booleans

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()

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 设置断点.

“compat” properties

Access of Module, Function, Class, Instance, File and Item through Node instances have long been documented as deprecated, but started to emit warnings from pytest 3.9 and onward.

Users should just import pytest and access those objects using the pytest module.