All Kubectl command should return array by default

app/models/clusters/applications/knative.rb

@@ -84,7 +84,7 @@ module Clusters
       private
       def delete_knative_services_and_metrics
-        delete_knative_services + delete_knative_istio_metrics.to_a
+        delete_knative_services + delete_knative_istio_metrics
       end
       def delete_knative_services
@@ -117,11 +117,15 @@ module Clusters
       end
       def install_knative_metrics
-        ["kubectl apply -f #{METRICS_CONFIG}"] if cluster.application_prometheus_available?
+        return [] unless cluster.application_prometheus_available?
+
+        ["kubectl apply -f #{METRICS_CONFIG}"]
       end
       def delete_knative_istio_metrics
-        ["kubectl delete --ignore-not-found -f #{METRICS_CONFIG}"] if cluster.application_prometheus_available?
+        return [] unless cluster.application_prometheus_available?
+
+        ["kubectl delete --ignore-not-found -f #{METRICS_CONFIG}"]
       end
       def verify_cluster?

app/models/clusters/applications/prometheus.rb

@@ -64,7 +64,7 @@ module Clusters
           name: name,
           rbac: cluster.platform_kubernetes_rbac?,
           files: files,
-          predelete: delete_knative_istio_metrics.to_a
+          predelete: delete_knative_istio_metrics
         )
       end
@@ -104,11 +104,15 @@ module Clusters
       end
       def install_knative_metrics
-        ["kubectl apply -f #{Clusters::Applications::Knative::METRICS_CONFIG}"] if cluster.application_knative_available?
+        return [] unless cluster.application_knative_available?
+
+        ["kubectl apply -f #{Clusters::Applications::Knative::METRICS_CONFIG}"]
       end
       def delete_knative_istio_metrics
-        ["kubectl delete -f #{Clusters::Applications::Knative::METRICS_CONFIG}"] if cluster.application_knative_available?
+        return [] unless cluster.application_knative_available?
+
+        ["kubectl delete -f #{Clusters::Applications::Knative::METRICS_CONFIG}"]
       end
     end
   end

spec/models/clusters/applications/knative_spec.rb

@@ -91,7 +91,7 @@ describe Clusters::Applications::Knative do
     end
     it 'does not install metrics for prometheus' do
-      expect(subject.postinstall).to be_nil
+      expect(subject.postinstall).to be_empty
     end
     context 'with prometheus installed' do
@@ -101,7 +101,7 @@ describe Clusters::Applications::Knative do
       subject { knative.install_command }
       it 'installs metrics' do
-        expect(subject.postinstall).not_to be_nil
+        expect(subject.postinstall).not_to be_empty
         expect(subject.postinstall.length).to be(1)
         expect(subject.postinstall[0]).to eql("kubectl apply -f #{Clusters::Applications::Knative::METRICS_CONFIG}")
       end

spec/models/clusters/applications/prometheus_spec.rb

@@ -142,7 +142,7 @@ describe Clusters::Applications::Prometheus do
     end
     it 'does not install knative metrics' do
-      expect(subject.postinstall).to be_nil
+      expect(subject.postinstall).to be_empty
     end
     context 'with knative installed' do