Pytest-Configuration

hogwarts · 2020 年11 月 30 日 09:19

Command line options and configuration file settings

You can get help on command line options and values in INI-style
configurations files by using the general help option:

pytest -h   # prints options _and_ config file settings

This will display command line and configuration file settings which
were registered by installed plugins.

Configuration file formats {#config file formats}

Many pytest settings <ini options ref>{.interpreted-text role=“ref”}
can be set in a configuration file, which by convention resides on the
root of your repository or in your tests folder.

A quick example of the configuration files supported by pytest:

pytest.ini

pytest.ini files take precedence over other files, even when empty.

# pytest.ini
[pytest]
minversion = 6.0
addopts = -ra -q
testpaths =
    tests
    integration

pyproject.toml

::: {.versionadded}
6.0
:::

pyproject.toml are considered for configuration when they contain a
tool.pytest.ini_options table.

# pyproject.toml
[tool.pytest.ini_options]
minversion = "6.0"
addopts = "-ra -q"
testpaths = [
    "tests",
    "integration",
]

::: {.note}
::: {.title}
Note
:::

One might wonder why [tool.pytest.ini_options] instead of
[tool.pytest] as is the case with other tools.

The reason is that the pytest team intends to fully utilize the rich
TOML data format for configuration in the future, reserving the
[tool.pytest] table for that. The ini_options table is being used,
for now, as a bridge between the existing .ini configuration system
and the future configuration format.
:::

tox.ini

tox.ini files are the configuration files of the
tox project, and can also be used to hold
pytest configuration if they have a [pytest] section.

# tox.ini
[pytest]
minversion = 6.0
addopts = -ra -q
testpaths =
    tests
    integration

setup.cfg

setup.cfg files are general purpose configuration files, used
originally by
distutils, and
can also be used to hold pytest configuration if they have a
[tool:pytest] section.

# setup.cfg
[tool:pytest]
minversion = 6.0
addopts = -ra -q
testpaths =
    tests
    integration

::: {.warning}
::: {.title}
Warning
:::

Usage of setup.cfg is not recommended unless for very simple use
cases. .cfg files use a different parser than pytest.ini and
tox.ini which might cause hard to track down problems. When possible,
it is recommended to use the latter files, or pyproject.toml, to hold
your pytest configuration.
:::

Initialization: determining rootdir and configfile{#rootdir} {#configfiles}

pytest determines a rootdir for each test run which depends on the
command line arguments (specified test files, paths) and on the
existence of configuration files. The determined rootdir and
configfile are printed as part of the pytest header during startup.

Here's a summary what pytest uses rootdir for:

Construct nodeids during collection; each test is assigned a
unique nodeid which is rooted at the rootdir and takes into
account the full path, class name, function name and parametrization
(if any).
Is used by plugins as a stable location to store project/test run
specific information; for example, the internal
cache <cache>{.interpreted-text role=“ref”} plugin creates a
.pytest_cache subdirectory in rootdir to store its cross-test
run state.

rootdir is NOT used to modify sys.path/PYTHONPATH or influence
how modules are imported. See pythonpath{.interpreted-text role=“ref”}
for more details.

The --rootdir=path command-line option can be used to force a specific
directory. Note that contrary to other command-line options, --rootdir
cannot be used with addopts{.interpreted-text role=“confval”} inside
pytest.ini because the rootdir is used to find pytest.ini
already.

Finding the `rootdir`

Here is the algorithm which finds the rootdir from args:

Determine the common ancestor directory for the specified args
that are recognised as paths that exist in the file system. If no
such paths are found, the common ancestor directory is set to the
current working directory.
Look for pytest.ini, pyproject.toml, tox.ini, and setup.cfg
files in the ancestor directory and upwards. If one is matched, it
becomes the configfile and its directory becomes the rootdir.
If no configuration file was found, look for setup.py upwards from
the common ancestor directory to determine the rootdir.
If no setup.py was found, look for pytest.ini, pyproject.toml,
tox.ini, and setup.cfg in each of the specified args and
upwards. If one is matched, it becomes the configfile and its
directory becomes the rootdir.
If no configfile was found, use the already determined common
ancestor as root directory. This allows the use of pytest in
structures that are not part of a package and don't have any
particular configuration file.

If no args are given, pytest collects test below the current working
directory and also starts determining the rootdir from there.

Files will only be matched for configuration if:

pytest.ini: will always match and take precedence, even if empty.
pyproject.toml: contains a [tool.pytest.ini_options] table.
tox.ini: contains a [pytest] section.
setup.cfg: contains a [tool:pytest] section.

The files are considered in the order above. Options from multiple
configfiles candidates are never merged - the first match wins.

The internal Config <_pytest.config.Config>{.interpreted-text
role=“class”} object (accessible via hooks or through the
pytestconfig{.interpreted-text role=“fixture”} fixture) will
subsequently carry these attributes:

config.rootpath <_pytest.config.Config.rootpath>{.interpreted-text
role=“attr”}: the determined root directory, guaranteed to exist.
config.inipath <_pytest.config.Config.inipath>{.interpreted-text
role=“attr”}: the determined configfile, may be None (it is
named inipath for historical reasons).

::: {.versionadded}
6.1 The config.rootpath and config.inipath properties. They are
pathlib.Path{.interpreted-text role=“class”} versions of the older
config.rootdir and config.inifile, which have type py.path.local,
and still exist for backward compatibility.
:::

The rootdir is used as a reference directory for constructing test
addresses ("nodeids") and can be used also by plugins for storing
per-testrun information.

Example:

pytest path/to/testdir path/other/

will determine the common ancestor as path and then check for
configuration files as follows:

# first look for pytest.ini files
path/pytest.ini
path/pyproject.toml  # must contain a [tool.pytest.ini_options] table to match
path/tox.ini         # must contain [pytest] section to match
path/setup.cfg       # must contain [tool:pytest] section to match
pytest.ini
... # all the way up to the root

# now look for setup.py
path/setup.py
setup.py
... # all the way up to the root