diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index 7653407a5..d7d402cbc 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -20,7 +20,7 @@ on:
       - submitted
 
 env:
-  MAIN_TESTDATA_BRANCH: main
+  XCLIM_TESTDATA_BRANCH: main
 
 jobs:
   black:
@@ -115,8 +115,9 @@ jobs:
           python -m pip install --no-user .
       - name: Test
         run: |
+          pip list
           pip check
-          pytest xclim --durations=10
+          pytest xclim --num-workers=logical --durations=10 --cov=xclim --cov-report=term-missing
         env:
           CONDA_EXE: mamba
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
@@ -184,10 +185,6 @@ jobs:
         run: pylint --rcfile=pylintrc --disable=import-error --exit-zero xclim
       - name: Test with tox
         run: tox -e notebooks_doctests
-      - name: Report coverage
-        run: |
-          pip install --upgrade coveralls
-          coveralls
         env:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
           COVERALLS_FLAG_NAME: run-notebooks_doctests-py38
diff --git a/pyproject.toml b/pyproject.toml
index 5d9f9cae8..c1bdfa15a 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -166,10 +166,8 @@ ignore_missing_imports = true
 addopts = [
   "--verbose",
   "--color=yes",
-  "--cov=xclim",
-  "--cov-report=term-missing",
-  "--numprocesses=auto",
-  "--maxprocesses=6",
+  "--numprocesses=0",
+  "--maxprocesses=8",
   "--dist=worksteal"
 ]
 norecursedirs = ["docs/notebooks/*"]
diff --git a/tox.ini b/tox.ini
index ce348df9c..d5e8df350 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,16 +1,15 @@
 [tox]
+min_version = 4.0
 env_list =
     black
     docs
-    notebooks_doctests
+    notebooks_doctests{-coverage,}
 ;    opt-slow
     py38-lm3
     py39-upstream-doctest
     py310-slow
-isolated_build = True
 requires =
     pip >= 21.0
-    tox ~=3.0
 opts = -v
 
 [testenv:black]
@@ -35,6 +34,7 @@ commands =
     blackdoc --check docs
     isort --check xclim
     yamllint --config-file=.yamllint.yaml xclim
+commands_post =
 
 [testenv:docs]
 description = Build the documentation with makefile under {basepython}
@@ -44,6 +44,7 @@ setenv =
     READTHEDOCS = 1
 commands =
     make docs
+commands_post =
 allowlist_externals =
     env
     make
@@ -55,11 +56,11 @@ allowlist_externals =
 ;conda_env = environment-dev.yml
 ;extras =
 
-[testenv:notebooks_doctests]
+[testenv:notebooks_doctests{-coverage,}]
 description = Run notebooks and doctests with pytest under {basepython}
 commands =
-    pytest --no-cov --nbval --dist=loadscope docs/notebooks --durations=10 --ignore=docs/notebooks/example.ipynb
-    pytest --rootdir xclim/testing/tests/ --xdoctest xclim --ignore=xclim/testing/tests/ --durations=10
+    pytest --no-cov --nbval --dist=loadscope docs/notebooks --ignore=docs/notebooks/example.ipynb
+    pytest --rootdir xclim/testing/tests/ --xdoctest xclim --ignore=xclim/testing/tests/
 
 # Requires tox-conda compatible with tox@v4.0
 ;[testenv:opt-{slow,not_slow}]
@@ -76,6 +77,8 @@ commands =
 description = Run tests with pytest under {basepython}
 setenv =
     COV_CORE_SOURCE =
+    PYTEST_ADDOPTS = --numprocesses=logical --durations=10
+    coverage: PYTEST_ADDOPTS = --numprocesses=logical --durations=10 --cov=xclim --cov-report=term-missing
     PYTHONPATH = {toxinidir}
 passenv =
     CI
@@ -83,7 +86,7 @@ passenv =
     COVERALLS_*
     GITHUB_*
     LD_LIBRARY_PATH
-    MAIN_TESTDATA_BRANCH
+    XCLIM_*
 extras = dev
 deps =
     coverage: coveralls
@@ -91,12 +94,14 @@ deps =
     upstream: -rrequirements_upstream.txt
 install_command = python -m pip install --no-user {opts} {packages}
 download = True
-commands =
+commands_pre =
     pip list
     pip check
-    doctest: pytest --no-cov --rootdir xclim/testing/tests/ --xdoctest xclim --ignore=xclim/testing/tests/ --durations=10
-    !slow: pytest xclim -m "not slow" --durations=10
-    slow: pytest xclim --durations=10
+commands =
+    doctest: pytest --no-cov --rootdir xclim/testing/tests/ --xdoctest xclim --ignore=xclim/testing/tests/
+    !slow: pytest xclim -m "not slow"
+    slow: pytest xclim
+commands_post =
     coverage: - coveralls
 allowlist_externals =
     git