Refactor used quota method and test

This PR is based on on the issue below.
ManageIQ/manageiq#12038

content/automate/ManageIQ/System/CommonMethods/QuotaMethods.class/__methods__/used.rb

@@ -2,14 +2,47 @@
 # Description: calculate entity used quota values
 #
 
-def consumption(source)
-  {
-    :cpu                 => source.allocated_vcpu,
-    :memory              => source.allocated_memory,
-    :vms                 => source.vms.count { |vm| vm.id if vm.ems_id },
-    :storage             => source.allocated_storage,
-    :provisioned_storage => source.provisioned_storage
-  }
+module ManageIQ
+  module Automate
+    module System
+      module CommonMethods
+        module QuotaMethods
+          class Used
+            def initialize(handle = $evm)
+              @handle = handle
+            end
+
+            def main
+              used(quota_source)
+            end
+
+            private
+
+            def used(quota_source)
+              @handle.root['quota_used'] = consumption(quota_source)
+            end
+
+            def quota_source
+              raise "ERROR - quota_source not found" unless @handle.root['quota_source']
+              @handle.root['quota_source']
+            end
+
+            def consumption(source)
+              {
+                :cpu                 => source.allocated_vcpu,
+                :memory              => source.allocated_memory,
+                :vms                 => source.vms.count { |vm| vm.id if vm.ems_id },
+                :storage             => source.allocated_storage,
+                :provisioned_storage => source.provisioned_storage
+              }
+            end
+          end
+        end
+      end
+    end
+  end
 end
 
-$evm.root['quota_used'] = consumption($evm.root['quota_source']) if $evm.root['quota_source']
+if __FILE__ == $PROGRAM_NAME
+  ManageIQ::Automate::System::CommonMethods::QuotaMethods::Used.new.main
+end

spec/content/automate/ManageIQ/System/CommonMethods/QuotaMethods.class/__methods__/used_spec.rb

@@ -0,0 +1,67 @@
+require_domain_file
+
+describe ManageIQ::Automate::System::CommonMethods::QuotaMethods::Used do
+  include Spec::Support::QuotaHelper
+
+  let!(:model) { setup_model }
+  let(:root_hash) do
+    {
+      'miq_provision_request' => @miq_provision_request,
+      'miq_request'           => @miq_provision_request,
+      'quota_source'          => quota_source,
+      'quota_source_type'     => quota_source_type
+    }
+  end
+
+  let(:counts_hash) do
+    {:storage => 1_000_000, :cpu => 0, :vms => 4, :memory => 1_073_741_824}
+  end
+
+  let(:root_object) do
+    Spec::Support::MiqAeMockObject.new(root_hash)
+  end
+
+  let(:ae_service) do
+    Spec::Support::MiqAeMockService.new(root_object).tap do |service|
+      current_object = Spec::Support::MiqAeMockObject.new
+      current_object.parent = root_object
+      service.object = current_object
+    end
+  end
+
+  shared_examples_for "used" do
+    it "check" do
+      described_class.new(ae_service).main
+      expect(ae_service.root['quota_used']).to include(counts_hash)
+    end
+  end
+
+  context "returns ok for tenant counts" do
+    let(:quota_source) { @tenant }
+    let(:quota_source_type) { 'tenant' }
+    it_behaves_like "used"
+  end
+
+  context "returns ok for user counts" do
+    let(:quota_source) { @tenant }
+    let(:quota_source_type) { 'user' }
+    it_behaves_like "used"
+  end
+
+  context "returns ok for group counts" do
+    let(:quota_source) { @tenant }
+    let(:quota_source_type) { 'group' }
+    it_behaves_like "used"
+  end
+
+  context "returns error " do
+    let(:quota_source_type) { nil }
+    let(:quota_source) { nil }
+    let(:status_and_message) { [true, ""] }
+    let(:errormsg) { 'ERROR - quota_source not found' }
+    it "when no quota source" do
+      allow(ae_service).to receive(:used).and_return(status_and_message)
+      expect { described_class.new(ae_service).main }.to raise_error(errormsg)
+    end
+  end
+end