diff --git a/.github/workflows/full_test.yml b/.github/workflows/full_test.yml
index 3ebc1ca7..4a1961d0 100644
--- a/.github/workflows/full_test.yml
+++ b/.github/workflows/full_test.yml
@@ -44,10 +44,10 @@ jobs:
         pip install .[test]
     - name: Test with pytest (basic)
       run: |
-        pytest -m ""
+        pytest -c .pytest-ci.ini 
     - name: Install mikeio1d (optional dependencies)
       run: |
         pip install .[all]
     - name: Test with pytest (optional dependencies)
       run: |
-        pytest -m ""
+        pytest -c .pytest-ci.ini 
diff --git a/.pytest-ci.ini b/.pytest-ci.ini
new file mode 100644
index 00000000..3cd290b0
--- /dev/null
+++ b/.pytest-ci.ini
@@ -0,0 +1,6 @@
+; this is the pytest configuration file used by the CI pipeline
+[pytest]
+addopts = 
+    --strict-markers
+markers =
+    slow
diff --git a/.pytest.ini b/.pytest.ini
index 84060a83..3be1ee55 100644
--- a/.pytest.ini
+++ b/.pytest.ini
@@ -1,3 +1,4 @@
+; this file is used locally and not in the CI pipeline - refer to .pytest-ci.ini for CI pipeline configuration
 [pytest]
 addopts = 
     --strict-markers