Update workflow

.github/workflows/testing.yml

@@ -0,0 +1,50 @@
+name: Testing
+
+on:
+  push:
+    branches: [ master ]
+  pull_request:
+    branches: [ master ]
+
+jobs:
+  build:
+
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        python-version: [ 3.8, 3.9 ]
+
+    steps:
+    - name: Checkout
+      uses: actions/checkout@v2
+
+    - name: Set up Python ${{ matrix.python-version }}
+      uses: actions/setup-python@v2
+      with:
+        python-version: ${{ matrix.python-version }}
+
+    - name: Install Poetry
+      uses: snok/install-poetry@v1
+      with:
+        virtualenvs-create: true
+        virtualenvs-in-project: true
+        installer-parallel: true
+
+    - name: Load cached venv
+      id: cached-poetry-dependencies
+      uses: actions/cache@v2
+      with:
+        path: .venv
+        key: venv-${{ runner.os }}-${{ hashFiles('**/poetry.lock') }}
+
+    - name: Install dependencies
+      if: steps.cached-poetry-dependencies.outputs.cache-hit != 'true'
+      run: poetry install --no-interaction --no-root
+
+    - name: Install library
+      run: poetry install --no-interaction
+
+    - name: Run tests
+      run: |
+        source .venv/bin/activate
+        pytest tests/