Added functionality to test multiple versions of python using tox (#994)

* Adding tox support

Adds tox support for testing against multiple versions of python

* PR etiquette comment

Add example of how to raise a PR.

* Add a comment about multi-version local testing

Adds a comment about how to run tests locally on multiple versions of python.

Ensures it is clear that it only works if particular version of python is installed on the users machine.

Recommends `pytest` as a possible way to manage multiple local versions of python.

Note the hyperlink out to `setup.cfg` is pinned to commit sha 1297c8c instead of pinning to main branch.

---------

Co-authored-by: Nils Braun <[email protected]>

.gitignore

@@ -61,3 +61,9 @@ tsfresh/notebooks/data/
 # dask
 dask-worker-space
 dask-worker-space/
+
+# python version files
+.python_version
+
+# tox log files
+.tox

docs/text/how_to_contribute.rst

@@ -67,6 +67,18 @@ you have to:
     pytest
 
 
+To test changes across multiple versions of Python, run:
+
+
+.. code::
+
+    tox -r
+
+
+`tox -r` will execute tests for the Python versions specified in `setup.cfg <https://github.com/blue-yonder/tsfresh/blob/1297c8ca5bd6f8f23b4de50e3f052fb4ec1307f8/setup.cfg>`_ using the `envlist` variable. For example, if `envlist` is set to `py37, py38`, the test suite will run for Python 3.7 and 3.8 on the local development platform, assuming the binaries for those versions are available locally. The exact Python microversions (e.g. `3.7.1` vs `3.7.2`) depend on what is installed on the local development machine.
+
+A recommended way to manage multiple Python versions when testing locally is with `pyenv`, which enables organized installation and switching between versions.
+
 Documentation
 '''''''''''''
 
@@ -90,3 +102,9 @@ We use black and isort for styling. They are automatically triggered on every co
 
 
 We are looking forward to hear from you! =)
+
+
+PR Descriptions
+'''''''''''''''
+
+The PR should have a clear and descriptive title, along with a detailed description of the changes made, the problem being addressed, and any relevant tips for reviewers. An example of what this might look like is `here. <https://github.com/blue-yonder/tsfresh/pull/994#issue-1509962136>`_

setup.cfg

@@ -140,3 +140,23 @@ max-line-length = 120
 # This will be used when updating. Do not change!
 version = 3.2.3
 package = tsfresh
+
+[tox:tox]
+# Tox global conifguration options
+minversion = 4.0.0
+# Which python versions to test for
+envlist = py37, py38, py39, py310, py311
+# Don't throw an error if a specific version of python is not installed
+skip_missing_interpreters = True
+# Ensure that tox uses a virtual environment to build a source distribution
+isolated_build = True
+
+# Tox configuration options for each version of python
+[testenv]
+commands =
+    # display the python version that tests are being run on
+    python -V
+    # install package requirements before running tests
+    python -m pip install .[testing]
+    # run the tests
+    python -m pytest tests/