add github workflow to run unit tests

.github/workflows/unit_test.yml

@@ -0,0 +1,33 @@
+name: tests
+
+on:
+  pull_request:
+      - main
+
+
+jobs:
+  test:
+    name: unit tests
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v2
+
+      - name: Setup Node.js
+        uses: actions/setup-node@v2
+        with:
+          node-version: 16
+
+      - name: Cache dependencies
+        id: yarn-cache
+        uses: actions/cache@v2
+        with:
+          path: '**/node_modules'
+          key: ${{ runner.os }}-node-modules-${{ hashFiles('**/yarn.lock') }}
+
+      - name: Install dependencies
+        if: steps.yarn-cache.outputs.cache-hit != 'true'
+        run: yarn install --frozen-lockfile
+
+      - name: run tests
+        run: yarn test