Use skip_install=true for tox.ini dev environment

tox.ini

@@ -14,16 +14,16 @@ commands = python -m pip install --upgrade pip
 # the tests environment is called by the Github action that runs the unit tests
 deps =
     -r requirements.txt
-    .[tests]
+extras = tests
 setenv = PYTHONPATH = {toxinidir}/src
 commands = python -m pytest --basetemp={envtmpdir} {posargs}
 
 [testenv:linting]
 # the linting environment is called by the Github Action that runs the linter
 deps =
     {[testenv:tests]deps}
-    .[linting]
-    # add your fixtures like e.g. pytest_datafiles here
+extras = linting
+allowlist_externals = pylint
 setenv = PYTHONPATH = {toxinidir}/src
 commands =
     pylint mypackage
@@ -35,7 +35,8 @@ commands =
 setenv = PYTHONPATH = {toxinidir}/src
 deps =
     {[testenv:tests]deps}
-    .[type_check]
+extras = type_check
+allowlist_externals = mypy
 commands =
     mypy --show-error-codes src/mypackage --strict
     mypy --show-error-codes unittests --strict
@@ -46,7 +47,8 @@ commands =
 setenv = PYTHONPATH = {toxinidir}/src
 deps =
     -r requirements.txt
-    .[spell_check]
+extras = spell_check
+allowlist_externals = codespell
 commands =
     codespell --ignore-words=domain-specific-terms.txt src
     codespell --ignore-words=domain-specific-terms.txt README.md
@@ -57,7 +59,8 @@ commands =
 changedir = unittests
 deps =
     {[testenv:tests]deps}
-    .[coverage]
+extras = coverage
+allowlist_externals = coverage
 setenv = PYTHONPATH = {toxinidir}/src
 commands =
     coverage run -m pytest --basetemp={envtmpdir} {posargs}
@@ -78,18 +81,17 @@ deps =
     {[testenv:type_check]deps}
     {[testenv:coverage]deps}
     {[testenv:spell_check]deps}
-    .[formatting]
-    .[dev]
     pre-commit
+extras = formatting, dev
+skip_install=true
 commands =
     python -m pip install --upgrade pip
     pip install -r requirements.txt
     pre-commit install
 
 [testenv:test_packaging]
 skip_install = true
-deps =
-    .[packaging]
+extras = packaging
 commands =
     python -m build
     twine check dist/*