use cache on test workflow

.github/workflows/publish.yml

@@ -16,8 +16,6 @@ jobs:
       - run: npm install -g yarn
       - name: Install dependencies
         run: yarn
-      # - name: Run tests
-      #   run: yarn test
       - id: publish
         uses: JS-DevTools/npm-publish@v1
         with:

.github/workflows/tests.yml

@@ -8,19 +8,36 @@ jobs:
     steps:
       - name: Checkout
         uses: actions/checkout@v1
+
       - name: Setup Node.js
         uses: actions/setup-node@v1
         with:
           node-version: 12
-      - run: npm install -g yarn
+
+      - name: Get yarn cache directory path
+        id: yarn-cache-dir-path
+        run: echo "::set-output name=dir::$(yarn cache dir)"
+
+      - name: Restore yarn cache
+        uses: actions/cache@v2
+        id: yarn-cache # use this to check for `cache-hit` (`steps.yarn-cache.outputs.cache-hit != 'true'`)
+        with:
+          path: ${{ steps.yarn-cache-dir-path.outputs.dir }}
+          key: ${{ runner.os }}-yarn-${{ hashFiles('**/yarn.lock') }}
+          restore-keys: |
+            ${{ runner.os }}-yarn-
+
       - name: Install dependencies
-        run: yarn
+        run: yarn --prefer-offline
+
       - name: Setup React Native environment
         run: |
           yarn add react-native@0.63.4
           yarn add react@16.13.1
+
       - name: Run tests
         run: yarn test --coverage
+
       - name: Coveralls
         uses: coverallsapp/github-action@master
         with: