CI: add codecov

.github/workflows/test_cov.yml

@@ -0,0 +1,46 @@
+# This is a basic workflow to help you get started with Actions
+
+name: coverage
+
+# Controls when the workflow will run
+on:
+  # Triggers the workflow on push or pull request events but only for the master branch
+  push:
+    branches: master
+  pull_request:
+    branches: master
+
+  # Allows you to run this workflow manually from the Actions tab
+  workflow_dispatch:
+
+# A workflow run is made up of one or more jobs that can run sequentially or in parallel
+jobs:
+
+  run-codecov:
+    runs-on: ubuntu-latest
+    timeout-minutes: 10
+    
+    strategy:
+      matrix:
+        python-version: [3.8.x]
+    
+    steps:
+    - name: Checkout master
+      uses: actions/checkout@v2
+      
+    - name: Setup Python
+      uses: actions/setup-python@v2
+      with:
+        python-version: ${{ matrix.python }}
+      
+    - name: Install dependencies
+      run: |
+        python -m pip install --upgrade pip
+        python -m pip install -r requirements/coverage.txt
+        
+    - name: Run test suite
+      run: |
+        python -m pytest --cov=redmail --cov-report=xml redmail/test
+        
+    - name: Upload test coverage
+      uses: codecov/codecov-action@v2