github: add unit-tests job

Signed-off-by: Simon Deziel <simon.deziel@canonical.com>

.github/workflows/tests.yml

@@ -33,6 +33,21 @@ jobs:
       run: |
         tox -e check
 
+  unit-tests:
+    name: Unit tests
+    runs-on: ubuntu-22.04
+    steps:
+    - name: Repository checkout
+      uses: actions/checkout@v4
+
+    - name: Install dependencies
+      run: |
+        pip install --upgrade pip tox
+
+    - name: Run unit tests
+      run: |
+        tox -e unit
+
   tests:
     name: Tests
     strategy: