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 Autouse fixtures (fixtures you don’t have to request)
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
andos
modules and the pytestconfig
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 Setting breakpoints.
“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.