Project Testing Interface: Python¶
Each project containing Python components must be able to do:
Unit tests for Python (see below for version details)
Codestyle checks
Testing Coverage Report
Source Tarball Generation
Translations import/export and merge for translated projects
Documentation generation
Specific commands¶
To drive the above tasks, the following commands should be supported in a clean tree:
tox -e pep8
tox -e cover
python -m build -s .
(sdist)python -m build -w .
(wheels)sphinx-build -W -b html doc/source doc/build
The Python 3 version may change from cycle to cycle. Projects should target the following, extending supported Python 3.x with the tested Python 3 runtimes for the current development cycle:
tox -e py3x
Projects should avoid removing Python versions that have not reached End Of Life without a solid reason. It is recommended to keep compatibility with older Python versions as long as possible. While CI coverage of Python versions that are not mentioned in PTI can be reduced, such reduction is not mandatory.
Projects that are translated should also support generating and updating their Portable Object Template (``.pot``) files using the following commands:
pybabel extract
pybabel update
Some basic prerequisites for test running (system packages, database
configuration, custom filesystem types) are acceptable as long as they are
documented in a visible location such as a CONTRIBUTING.rst
,
TESTING.rst
, or README.rst
file in the root of the repository.
Requirements Listing¶
Each project should list its required dependencies in either
project.dependencies
in pyproject.toml
or in a requirements.txt
file, while additional dependencies required for testing should be listed in
the test
key of project.optional-dependencies
in pyproject.toml
or
in a test-requirements.txt
file.
Environment marker should be used if there are requirements that are
specific to a given Python version, platform (Windows, Linux, …), or
implementation (cpython, pypy, …)
Constraints¶
The requirements project maintains a set of constraints with packages pinned to specific package versions that are known to be working. The goal is to ease the diagnosis of breakage caused by projects upstream to OpenStack and to provide a set of packages known to work together.
Projects may opt into using the constraints in one or more of their
standard targets via their tox.ini
configuration.
Virtual Environment Management¶
To support sensible testing across multiple Python versions, we use tox config files in the projects.
Python test running¶
OpenStack uses stestr as its test runner. stestr should be used for running all Python tests, including unit, functional, and integration tests. stestr is used because of its real time subunit output and its support for parallel execution of tests. In addition, stestr only runs tests conforming to the Python stdlib unittest model (and extensions on it like testtools). This enables people to use any test runner they prefer locally. Other popular test runners often include a testing ecosystem which is tied directly to the runner. Using these precludes the use of alternative runners for other users.
To have a consistent interface via tox between projects’ unit test jobs the command for running stestr in tox should be set like so:
[testenv]
commands =
stestr run {posargs}
Note
While the use of wrapper scripts can sometimes be useful as a short term crutch to work around a specific temporary issues, it should be avoided because it creates a divergent experience between projects, and can mask real issues.
If there are additional mandatory arguments needed for running a test suite they can be added before the positional arguments, ensuring the end user experience remains the same. For example:
[testenv]
commands =
stestr --test-path ./tests/unit run {posargs}
However, these arguments should try to be minimized because it just adds to the complexity that people will need to understand when running tests on a project.
Coverage Jobs¶
For coverage jobs you need to invoke the test runner in the same way as for the
normal unit test jobs, but to switch the Python executable to be
coverage run
. To do this you need to setup the tox cover
job like:
[testenv:cover]
setenv =
PYTHON=coverage run --source $project --parallel-mode
commands =
stestr run {posargs}
coverage combine
coverage html -d cover
coverage xml -o cover/coverage.xml
Specifically, the output html directory cover
and the coverage.xml
file
added to that directory are mandatory output artifacts.
Project Configuration¶
All OpenStack projects use pbr for consistent operation of setuptools.
To accomplish this, all setup.py
files only contain a simple setup function
that enabled pbr. Actual project configuration is then handled in
pyproject.toml
or setup.cfg
.
Generated Files¶
ChangeLog
and AUTHORS
files are generated at setup.py sdist time. This
is handled by pbr.
.mailmap
files should exist where a developer has more than one email
address or identity, and should map to the developer’s canonical identity.
Translations¶
To support translations processing, projects should have a valid babel config.
There should be a locale
package inside of the top project module, and in that
directory should be the $project.pot
file. For instance, the .pot
file
for nova should be found at nova/locale/nova.pot
. Babel commands should be
configured out output their .mo
files in to $project/locale
as well.
Release Notes¶
As a convenience for developers, it is recommended that projects provide
a releasenotes
environment for tox that will run
sphinx-build -a -E -W -d releasenotes/build/doctrees -b html \
releasenotes/source releasenotes/build/html
The project infrastructure will not use tox -e releasenotes
to build the
documentation. Therefore it is STRONGLY discouraged for people to put
additional logic into the command section of that tox environment. Additional
logic needed around release notes generation should go into reno.