Add Thetis smoke tests (#4198)

Author: cpjordan

.github/workflows/build.yml

@@ -170,6 +170,15 @@ jobs:
             gusto-repo/integration-tests/transport/test_embedded_dg_advection.py
         timeout-minutes: 10
 
+      - name: Run Thetis smoke tests
+        if: (success() || steps.install.conclusion == 'success') && matrix.arch == 'default'
+        run: |
+          . venv/bin/activate
+          git clone --depth 1 https://github.com/thetisproject/thetis.git thetis-repo
+          pip install --verbose ./thetis-repo
+          python -m pytest -n 8 --verbose thetis-repo/test_adjoint/test_swe_adjoint.py
+        timeout-minutes: 10
+
       - name: Run spyro smoke tests
         if: (success() || steps.install.conclusion == 'success') && matrix.arch == 'default'
         run: |