refactor: add a testing github action

.github/workflows/testing.yaml

@@ -0,0 +1,59 @@
+name: Testing
+
+on: [push, pull_request]
+
+jobs:
+  test:
+    strategy:
+      fail-fast: true
+      matrix:
+        os: [ "ubuntu-latest"]
+        python-version: [ "3.8", "3.9", "3.10", "3.11", "3.12" ]
+    runs-on: ${{ matrix.os }}
+    steps:
+      #----------------------------------------------
+      #       check-out repo and set-up python
+      #----------------------------------------------
+      - name: Check out repository
+        uses: actions/checkout@v4
+      - name: Set up python ${{ matrix.python-version }}
+        id: setup-python
+        uses: actions/setup-python@v5
+        with:
+          python-version: ${{ matrix.python-version }}
+      #----------------------------------------------
+      #  -----  install & configure poetry  -----
+      #----------------------------------------------
+      - name: Install Poetry
+        uses: snok/install-poetry@v1
+        with:
+          virtualenvs-create: true
+          virtualenvs-in-project: true
+      #----------------------------------------------
+      #       load cached venv if cache exists
+      #----------------------------------------------
+      - name: Load cached venv
+        id: cached-poetry-dependencies
+        uses: actions/cache@v3
+        with:
+          path: .venv
+          key: venv-${{ runner.os }}-${{ steps.setup-python.outputs.python-version }}-${{ hashFiles('**/poetry.lock') }}
+      #----------------------------------------------
+      # install dependencies if cache does not exist
+      #----------------------------------------------
+      - name: Install dependencies
+        if: steps.cached-poetry-dependencies.outputs.cache-hit != 'true'
+        run: poetry install --no-interaction --no-root
+      #----------------------------------------------
+      # install your root project, if required
+      #----------------------------------------------
+      - name: Install library
+        run: poetry install --no-interaction
+      #----------------------------------------------
+      #    add matrix specifics and run test suite
+      #----------------------------------------------
+      - name: Run tests
+        run: |
+          source .venv/bin/activate
+          pytest tests/
+          coverage report