tox plugin to run tests in current Python environment
The tox-current-env
plugin adds these options:
tox --current-env
- Runs the tox testenv's
commands
in the current Python environment (that is, the environment wheretox
is invoked from and installed in). Unlike regulartox
invocation, this installs no dependencies declared indeps
. An attempt to run this with a Python version that doesn't match will fail (iftox
is invoked from an Python 3.7 environment, any non 3.7 testenv will fail). tox --print-deps-to=FILE
- Instead of running any
commands
, simply prints the declared dependencies indeps
to the specifiedFILE
. This is useful for preparing the current environment fortox --current-env
. Use-
forFILE
to print to standard output. tox --print-extras-to=FILE
- Instead of running any
commands
, simply prints the names of the declared extras inextras
to the specifiedFILE
. This is useful for preparing the current environment fortox --current-env
. Use-
forFILE
to print to standard output.
It is possible to use the two printing options together, as long as the FILE
is different.
Invoking tox
without any of the above options should behave as regular tox
invocation without this plugin.
Any deviation from this behavior is considered a bug.
The plugin disables tox's way of providing a testing environment,
but assumes that you supply one in some other way.
Always run tox
with this plugin in a fresh isolated environment,
such as Python virtualenv, Linux container or chroot.
See other caveats below.
Obviously, tox
was created to run tests in isolated Python virtual environments.
The --current-env
flag totally defeats the purpose of tox
.
Why would anybody do that, you might ask?
Well, it turns out that tox
became too popular and gained another purpose.
The Python ecosystem now has formal specifications for many pieces of package metadata like versions or dependencies.
However, there is no standardization yet for declaring test dependencies or running tests.
The most popular de-facto standard for that today is tox
,
and we expect a future standard to evolve from tox.ini
.
This plugin lets us use tox
's dependency lists and testing commands for environments other than Python venvs.
We hope this plugin will enable community best practices around tox
configuration
to grow to better accomodate non-virtualenv environments in general – for example,
Linux distros, Conda, or containers.
Specifically, this plugin was created for Fedora's needs. When we package Python software as RPM packages, we try to run the project's test suite during package build. However, we need to test if the software works integrated into Fedora, not with packages downloaded from PyPI into a fresh environment. By running the tests in current environment, we can achieve that.
If you are interested in the RPM packaging part of this, see Fedora's %pyproject RPM macros.
Install this via pip
:
$ python -m pip install tox-current-env
Or install the development version by cloning the git repository
and pip
-installing locally:
$ git clone https://github.com/fedora-python/tox-current-env
$ cd tox-current-env
$ python -m pip install -e .
When the plugin is installed,
use tox
with --current-env
, --print-deps-to
or --print-extras-to
and all the other options as usual.
Assuming your tox
is installed on Python 3.7:
$ tox -e py37 --current-env
py37 create: /home/pythonista/projects/holy-grail/tests/.tox/py37
py37 installed: ...list of packages from the current environment...
py37 run-test-pre: PYTHONHASHSEED='3333333333'
py37 run-test: commands...
...runs tests in current environment's Python...
___________________________________ summary ____________________________________
py37: commands succeeded
congratulations :)
Attempting to run the py36
environment's test will fail:
$ tox -e py36 --current-env
py36 create: /home/pythonista/projects/holy-grail/tests/.tox/py36
ERROR: InterpreterMismatch: tox_current_env: interpreter versions do not match:
in current env: (3, 7, 4, 'final', 0)
requested: (3, 6, 9, 'final', 0)
___________________________________ summary ____________________________________
ERROR: py36: InterpreterMismatch: tox_current_env: interpreter versions do not match:
in current env: (3, 7, 4, 'final', 0)
requested: (3, 6, 9, 'final', 0)
To get list of test dependencies, run:
$ tox -e py37 --print-deps-to -
py37 create: /home/pythonista/projects/holy-grail/tests/.tox/py37
py37 installed: ...you can see almost anything here...
py37 run-test-pre: PYTHONHASHSEED='3333333333'
dep1
dep2
...
___________________________________ summary ____________________________________
py37: commands succeeded
congratulations :)
To get a list of names of extras, run:
$ tox -e py37 --print-extras-to -
py37 create: /home/pythonista/projects/holy-grail/tests/.tox/py37
py37 installed: ...you can see almost anything here...
py37 run-test-pre: PYTHONHASHSEED='3333333333'
extra1
extra2
...
___________________________________ summary ____________________________________
py37: commands succeeded
congratulations :)
The plugin is available also for tox 4. Differences in behavior between tox 3 and 4 are these:
--recreate
is no longer needed when you switch from the plugin back to standard tox. Tox detects it and handles the recreation automatically.- The plugin does not check the requested Python version nor the environment name. If you let it run for multiple environments they'll all use the same Python.
- Deprecated
--print-deps-only
option is no longer available.
Running (especially third party software's) tests in your system Python environment is dangerous. Always use this plugin in an isolated environment, such as a Linux container, virtual machine or chroot. You have been warned.
In order to support the python
command in the commands
section,
the current environment invocation of tox
creates a fake virtual environment
that just has a symbolic link to the Python executable.
The link is named python
even if the real interpreter's name is different
(such as python3.7
or pypy
).
Any other commands are not linked anywhere and it is the users' responsibility
to make sure such commands are in $PATH
and use the correct Python.
This can lead to slightly different results of tests than invoking them directly,
especially if you have assumptions about sys.executable
or other commands
in your tests.
As a specific example, tests should invoke python -m pytest
rather than assuming
the pytest
command is present and uses the correct version of Python.
tox caches the virtualenvs it creates, and doesn't distinguish between
regular virtualenvs and --current-env
.
Don't mix tox --current-env
, tox --print-deps-to
or tox --print-extras-to
runs and regular tox
runs (without the flags provided by this plugin).
If you ever need to do this, use tox's --recreate/-r
flag to clear the cache.
The plugin should abort with a meaningful error message if this is detected,
but in some corner cases (such as running tox --current-env
,
forcefully killing it before it finished, uninstalling the plugin,
and running tox
), you will get undefined results
(such as installing packages from PyPI into your current environment).
Since 0.0.9, all Shell environment variables are passed by default when using this plugin. The passenv tox configuration is set to *. Read the documentation for more information about passing environment variables to tox.
The tested projects can specify the
minimal tox version
and/or
additional requires
needed in the environment where tox
is installed.
Normally, tox
uses provisioning when such requirements are not met.
It creates a virtual environment,
installs (a newer version of) tox
and the missing packages
into that environment and proxies all tox
invocations trough that.
Unfortunately, this is undesired for tox-current-env
.
- It is possible to invoke
tox
with--no-provision
to prevent the provision entirely. When requirements are missing,tox
fails instead of provisioning. If a path is passed as a value for--no-provision
, the requirements will be serialized to the file, as JSON.- The requires, if specified, are included in the results of
tox --print-deps-to
. This only works when they are installed (otherwise see the first point).- The minimal tox version, if specified, is included in the results of
tox --print-deps-to
. This only works when the version requirement is satisfied (otherwise see the first point).
The recommend way to handle this is:
- Run
tox --no-provision provision.json --print-deps-to=...
or similar.- If the command fails, install requirements from
provision.json
to the current environment and try again.
Note that the specified requirements are likely to contain
other tox plugins
and many of them might interfere with tox-current-env
in an undesired way.
If that is the case, the recommended way is to patch/sed such undesired plugins
out of the configuration before running tox
.
The installed:
line in the output of tox --print-deps-to
/tox --print-extras-to
shows irrelevant output
(based on the content of the real or faked virtual environment).
Regardless of any Python flags used in the shebang of tox
,
the tests are invoked with sys.executable
without any added flags
(unless explicitly invoked with them in the commands
section).
The current environment's Python is tested for the major and minor version only. Different interpreters with the same Python version (such as CPython and PyPy) are treated as equal.
Only Linux is supported, with special emphasis on Fedora. This plugin might work on other Unix-like systems, but does not work on Microsoft Windows.
This is alpha quality software. Use it at your on your own risk. Pull requests with improvements are welcome.
The development happens on GitHub, at the fedora-python/tox-current-env repository. You can use the issue tracker there for any discussion or send Pull Requests.
In order to run the tests, you'll need tox
and Python from 3.6 to 3.10 installed.
The integration tests assume all of them are available.
On Fedora, you just need to dnf install tox
.
Run tox
to invoke the tests.
Running tests of this plugin with its own --current-env
flag will most likely blow up.
The tox-current-env
project is licensed under the so-called MIT license, full text available in the LICENSE file.
The tox-current-env
project follows the Fedora's Code of Conduct.