add reusable workflows

.github/workflows/UnitTesting.yml

@@ -0,0 +1,54 @@
+name: Unit Testing
+
+on:
+  workflow_call:
+    inputs:
+      TestReport:
+        description: "Generate unit test report with junitxml and upload results as an artifact."
+        required: false
+        default: false
+        type: string
+
+jobs:
+
+  UnitTesting:
+    name: ${{ matrix.icon }} Unit Tests using Python ${{ matrix.python }}
+    runs-on: ubuntu-latest
+
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+#          - {python: "3.6",  icon: 🔴} # until 23.12.2021
+          - {python: "3.7",  icon: 🟠} # until 27.06.2023
+          - {python: "3.8",  icon: 🟡} # until Oct. 2024
+          - {python: "3.9",  icon: 🟢} # until Oct. 2025
+          - {python: "3.10", icon: 🟢} # until Oct. 2026
+
+    steps:
+      - name: ⏬ Checkout repository
+        uses: actions/checkout@v2
+
+      - name: 🐍 Setup Python ${{ matrix.python }}
+        uses: actions/setup-python@v2
+        with:
+          python-version: ${{ matrix.python }}
+
+      - name: 🔧 Install dependencies
+        run: |
+          python -m pip install --upgrade pip
+          pip install -r tests/requirements.txt
+
+      - name: ☑ Run unit tests
+        run: |
+          [ '${{ inputs.TestReport }}' = 'true' ] && PYTEST_ARGS='--junitxml=TestReport.xml' || unset PYTEST_ARGS
+          python -m pytest -rA tests/unit $PYTEST_ARGS --color=yes
+
+      - name: 📤 Upload 'TestReport.xml' artifact
+        if: inputs.TestReport == 'true'
+        uses: actions/upload-artifact@v2
+        with:
+          name: TestReport-${{ matrix.python }}
+          path: TestReport.xml
+          if-no-files-found: error
+          retention-days: 1