Add running the unittests to the GitHub workflow

.github/workflows/default.yml

@@ -1,4 +1,4 @@
-# (C) Crown Copyright 2022-2025, Met Office.
+# (C) Crown Copyright 2022-2026, Met Office.
 # The LICENSE.md file contains full licensing details.
 # This workflow creates the required Conda environment, performs various
 # validation steps for Cylc and Rose, and builds and checks the documentation.
@@ -67,6 +67,11 @@ jobs:
           cd CMEW
           rose metadata-check -C meta/
 
+      - name: Run Cylc unit tests
+        run: |
+          cd CMEW
+          conda run -n cmew cylc vip -O metoffice -O unittest .
+
       - name: Build documentation
         run: |
           eval "$(conda shell.bash hook)"
@@ -93,3 +98,10 @@ jobs:
         run: |
           find . -type f \( -name "*.sh" -or -name "*-env$" \) \
           -exec shellcheck {} \;
+
+      - name: Upload cylc-run logs on failure
+        if: failure()
+        uses: actions/upload-artifact@v4
+        with:
+          name: cylc-run-logs
+          path: ~/cylc-run