Refactor redhat_best_fit_cluster method for VM Placement.

Refactored method and created test.

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

@miq-bot add_label refactoring
@miq-bot assign @tinaafitz
Fixed description

content/automate/ManageIQ/Infrastructure/VM/Provisioning/Placement.class/__methods__/redhat_best_fit_cluster.rb

@@ -1,22 +1,56 @@
 #
 # Description: This method sets the cluster based on source template
 #
+module ManageIQ
+  module Automate
+    module Infrastructure
+      module VM
+        module Provisioning
+          module Placement
+            class RedhatBestFitCluster
+              def initialize(handle = $evm)
+                @handle = handle
+              end
 
-# Get variables
-prov = $evm.root["miq_provision"]
-vm = prov.vm_template
-raise "VM not specified" if vm.nil?
-user = prov.miq_request.requester
-raise "User not specified" if user.nil?
-ems  = vm.ext_management_system
-raise "EMS not found for VM [#{vm.name}" if ems.nil?
+              def main
+                best_fit_cluster
+              end
 
-$evm.log("info", "vm=[#{vm.name}]")
+              private
 
-cluster = vm.ems_cluster
-$evm.log("info", "Selected Cluster: [#{cluster.nil? ? "nil" : cluster.name}]")
+              def request
+                @handle.root["miq_provision"].tap do |req|
+                  raise "miq_provision not specified" if req.nil?
+                end
+              end
 
-# Set cluster
-prov.set_cluster(cluster) if cluster
+              def vm
+                vm_obj = request.vm_template.tap do |vm|
+                  raise "VM not specified" if vm.nil?
+                end
+                vm_obj.ext_management_system.tap do |ems|
+                  raise 'ext_management_system not specified' if ems.nil?
+                end
+                vm_obj
+              end
 
-$evm.log("info", "vm=[#{vm.name}] cluster=[#{cluster}]")
+              def best_fit_cluster
+                @handle.log("info", "vm=[#{vm.name}]")
+
+                cluster = vm.ems_cluster
+                @handle.log("info", "Selected Cluster: [#{cluster.nil? ? "nil" : cluster.name}]")
+
+                # Set cluster
+                request.set_cluster(cluster) if cluster
+
+                @handle.log("info", "vm=[#{vm.name}] cluster=[#{cluster}]")
+              end
+            end
+          end
+        end
+      end
+    end
+  end
+end
+
+ManageIQ::Automate::Infrastructure::VM::Provisioning::Placement::RedhatBestFitCluster.new.main

spec/content/automate/ManageIQ/Infrastructure/VM/Provisioning/Placement.class/__methods__/redhat_best_fit_cluster_spec.rb

@@ -0,0 +1,41 @@
+require_domain_file
+
+describe ManageIQ::Automate::Infrastructure::VM::Provisioning::Placement::RedhatBestFitCluster do
+  let(:datacenter)  { FactoryBot.create(:datacenter, :ext_management_system => ems) }
+  let(:ems)         { FactoryBot.create(:ems_redhat_with_authentication) }
+  let(:ems_cluster) { FactoryBot.create(:ems_cluster, :ext_management_system => ems) }
+  let(:miq_provision) do
+    FactoryBot.create(:miq_provision_redhat,
+                      :options      => {:src_vm_id => vm_template.id, :placement_auto => [true, 1]},
+                      :userid       => user.userid,
+                      :source       => vm_template,
+                      :request_type => 'clone_to_vm',
+                      :state        => 'active',
+                      :status       => 'Ok')
+  end
+  let(:user)        { FactoryBot.create(:user_with_group, :settings => {:display => {:timezone => 'UTC'}}) }
+  let(:vm_template) { FactoryBot.create(:template_redhat, :ext_management_system => ems) }
+
+  let(:svc_miq_provision) { MiqAeMethodService::MiqAeServiceMiqProvision.find(miq_provision.id) }
+  let(:root_object) { Spec::Support::MiqAeMockObject.new(:miq_provision => svc_miq_provision) }
+  let(:ae_service)  { Spec::Support::MiqAeMockService.new(root_object) }
+
+  it 'Check log messages with No errors' do
+    expect(ae_service).to receive(:log).with('info', "vm=[#{vm_template.name}]")
+    expect(ae_service).to receive(:log).with('info', "Selected Cluster: [nil]")
+    expect(ae_service).to receive(:log).with('info', "vm=[#{vm_template.name}] cluster=[]")
+    described_class.new(ae_service).main
+  end
+
+  it 'Raise error when source vm is not specified' do
+    miq_provision.update(:source => nil)
+    expect { described_class.new(ae_service).main }.to raise_error('VM not specified')
+  end
+
+  context "Raise error" do
+    let(:svc_miq_provision) { nil }
+    it 'when miq_provision is not specified' do
+      expect { described_class.new(ae_service).main }.to raise_error('miq_provision not specified')
+    end
+  end
+end