add retro-compatibility test

Author: lalepee

.github/workflows/retro_copat_test.yml

@@ -0,0 +1,29 @@
+name: Run Tests
+
+on:
+  push:
+    branches: [ main ]
+  pull_request:
+    branches: [ main ]
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v3
+
+    - name: Set up Python
+      uses: actions/setup-python@v4
+      with:
+        python-version: '3.11'
+
+    - name: Install dependencies
+      run: |
+        python -m pip install --upgrade pip
+        pip install -e ".[test]"
+        pip install -e ".[past]"
+
+    - name: Run tests with coverage
+      run: |
+        pytest tests/unit/coal/ --cov=cosmotech.coal --cov-report=term