Add Helm chart unittests to CI (ray-project#3280)

Signed-off-by: Yi Chen <github@chenyicn.net>

Author: ChenYi015

.github/workflows/helm-lint.yaml

@@ -3,12 +3,12 @@ name: Lint and Test Charts
 on:
   push:
     branches:
-    - master
-    - release-*
+      - master
+      - release-*
   pull_request:
     branches:
-    - master
-    - release-*
+      - master
+      - release-*
 
 jobs:
   lint-test-helm-3-4:
@@ -28,6 +28,18 @@ jobs:
         with:
           python-version: 3.7
 
+      - name: Install Helm unittest plugin
+        run: helm plugin install https://github.com/helm-unittest/helm-unittest.git --version 0.8.1
+
+      - name: Run Helm unittest (kuberay-apiserver)
+        run: helm unittest helm-chart/kuberay-apiserver --file "tests/**/*_test.yaml" --strict --debug
+
+      - name: Run Helm unittest (kuberay-operator)
+        run: helm unittest helm-chart/kuberay-operator --file "tests/**/*_test.yaml" --strict --debug
+
+      - name: Run Helm unittest (ray-cluster)
+        run: helm unittest helm-chart/ray-cluster --file "tests/**/*_test.yaml" --strict --debug
+
       - name: Set up chart-testing
         uses: helm/chart-testing-action@v2.3.0
 
@@ -54,6 +66,18 @@ jobs:
         with:
           python-version: 3.7
 
+      - name: Install Helm unittest plugin
+        run: helm plugin install https://github.com/helm-unittest/helm-unittest.git --version 0.8.1
+
+      - name: Run Helm unittest (kuberay-apiserver)
+        run: helm unittest helm-chart/kuberay-apiserver --file "tests/**/*_test.yaml" --strict --debug
+
+      - name: Run Helm unittest (kuberay-operator)
+        run: helm unittest helm-chart/kuberay-operator --file "tests/**/*_test.yaml" --strict --debug
+
+      - name: Run Helm unittest (ray-cluster)
+        run: helm unittest helm-chart/ray-cluster --file "tests/**/*_test.yaml" --strict --debug
+
       - name: Set up chart-testing
         uses: helm/chart-testing-action@v2.3.0