TST: add pytest-* deps for dev job

tox.ini

@@ -28,6 +28,14 @@ deps =
     dev: matplotlib>=0.0.dev0
     dev: git+https://github.com/contourpy/contourpy.git
     dev: git+https://github.com/pandas-dev/pandas.git
+    dev: coverage
+    dev: flake8
+    dev: iniconfig
+    dev: mccabe
+    dev: packaging
+    dev: pluggy
+    dev: pycodestyle
+    dev: pyflakes
     lts: astropy==5.0.*
     lts: matplotlib==3.5.*
     # Pin numpy-lts until permanent solution for #2353/#2428
@@ -51,7 +59,8 @@ extras =
     all: all
     docs: docs
     visual: visualtest
-# Need `--no-deps` as long as pandas and contours have no branch for numpy>=2.0
+# Need `--no-deps` as long as pandas and contours have no branch for numpy>=2.0 -
+# for as long all pytest deps need to be manually pulled in above as well!
 install_command =
     !dev: python -I -m pip install
     dev: python -I -m pip install -v --pre --no-deps