Github tests

.github/workflows/tests.yaml

@@ -11,6 +11,7 @@ jobs:
     strategy:
       matrix:
         node-version: [8.x, 10.x, 12.x]
+        mongodb-version: [4.0, 4.2]
     steps:
     - uses: actions/checkout@v2
     - name: Use Node.js ${{ matrix.node-version }}
@@ -26,4 +27,5 @@ jobs:
     - name: npm test
       run: npm run test
       env:
-        test: true
+        test: true
+        CI: true