Rejig tox test running to remove tox-conda

tox-conda doesn't work with tox 4, and is becoming so out of date that
recent versions of Python and other dependencies start failing.
I couldn't get a working combination of dependencies on Python 3.12.

Author: mx-moth

docs/testing.rst

@@ -8,37 +8,48 @@ Python tests use the `pytest`_ framework,
 `flake8`_ and `isort`_ check the code formatting,
 and the documentation is build using `sphinx`_
 
-Setup
-=====
+Using tox
+=========
 
-To install all the testing tools,
-install ``emsarray`` in to a virtual environment with the ``[testing]`` extra.
+The easiest way to install all the test requirements is using Conda:
 
-.. code-block:: shell-session
+* Make a new Conda environment,
+* install the required packages using the provided environment file,
+* install Python and tox.
 
-    $ python3 -m venv venv
-    $ source venv/bin/activate
-    $ pip3 install --upgrade pip
-    $ pip3 install -r requirements.txt -e .[testing]
+.. code-block:: shell-session
 
-Running all the tests
-=====================
+    $ conda env create --name 'emsarray-tests-py3.12' --file continuous-integration/environment.yaml
+    $ conda activate emsarray-tests-py3.12
+    $ conda install -c conda-forge python==3.12 tox
 
 Invoke ``tox`` to run all the tests:
 
 .. code-block:: shell-session
 
-    $ tox
+    $ tox run -e py312-pytest-latest py312-pytest-pinned lint docs
 
-Running Python tests
-====================
+Note that this should only be used to run tests for the version of Python you
+installed in your Conda environment.
+
+Using pytest
+============
 
 You can invoke ``pytest`` directly to run just a subset of the tests.
-For example, to only run the tests in ``tests/operations.py``:
+Set up a new Conda environment, then install `emsarray` with the `testing` extra:
+
+.. code-block:: shell-session
+
+   $ conda env create --name 'emsarray-development' --file continuous-integration/environment.yaml
+   $ conda activate emsarray-development
+   $ conda install -c conda-forge python=3.12 pip
+   $ pip install -e .[testing]
+
+Invoke ``pytest`` to run the tests:
 
 .. code-block:: shell-session
 
-    $ pytest tests/test_operations.py
+    $ pytest
 
 .. _tox: https://tox.wiki/
 .. _pytest: https://pytest.org/

tox.ini

@@ -3,35 +3,26 @@ isolated_build = true
 package = wheel
 wheel_build_env = .pkg
 envlist =
-	py{310,311,312}-pytest-locked
+	py{310,311,312}-pytest-pinned
+	py310-pytest-minimum
 	py312-pytest-latest
 	lint,docs
 skip_missing_interpreters = true
-requires =
-  tox-conda
 
 [testenv]
 setenv =
 	# Conda doesn't isolate its environment from ~/.local,
 	# which can lead to strange conflicts
 	PYTHONNOUSERSITE = 1
 sitepackages = false
+passenv =
+	UDUNITS2_XML_PATH
 
-# Install some binary packages through conda
-conda_channels = conda-forge
-conda_install_args = --override-channels
-conda_deps =
-	pip
-	wheel
-	geos ~= 3.10.2
-	udunits2 >=2.2.25
-
-# Install the python dependencies through pip
-deps = -rcontinuous-integration/requirements.txt
-
-[testenv:py{39,310,311}-pytest-{locked,latest}]
+[testenv:py{310,311,312}-pytest-{pinned,latest,minimum}]
+description = "Run the pytest test suite against a specific Python version and dependencies"
 deps =
-	locked: -rcontinuous-integration/requirements.txt
+	pinned: -rcontinuous-integration/requirements.txt
+	minimum: -rcontinuous-integration/requirements-minimum.txt
 extras =
 	latest: testing
 commands =
@@ -44,15 +35,15 @@ setenv =
 	EMSARRAY_DATA_DIR = {envtmpdir}/emsarray_tutorial
 
 [testenv:lint]
-basepython = python3.12
-skip_install = true
+description = "Run the lint checkers"
+extras = testing
 commands =
 	isort --diff --check-only src/ tests/
 	flake8 src/ tests/
 	mypy --junit-xml report-mypy.xml src/
 
 [testenv:docs]
-basepython = python3.12
-skip_install = true
+description = "Build the docs"
+extras = complete,docs
 changedir = docs/
 commands = sphinx-build -b html -aEW . _build/html