Add test cases.

https://bugzilla.redhat.com/show_bug.cgi?id=1535237

spec/models/miq_provision/state_machine_spec.rb

@@ -151,5 +151,29 @@
         template.reload.with_relationship_type("genealogy")  { |v| expect(v.children).to eq([vm]) }
       end
     end
+
+    context "#log_last_worker" do
+      let(:server) { FactoryGirl.create(:miq_server, :name => "test_server", :zone => FactoryGirl.create(:zone)) }
+      let(:worker) { FactoryGirl.create(:miq_worker, :miq_server => server) }
+
+      it "logs worker/server info with last_worker_id in phase_context" do
+        task.update_attributes(:phase_context => {:last_worker_id => worker.id})
+        expect($log).to receive(:info).with(/Task was previously processed by Worker id:.*Server id/)
+        task.log_last_worker
+      end
+
+      it "logs worker id with worker does not exist" do
+        task.update_attributes(:phase_context => {:last_worker_id => worker.id})
+        expect($log).to receive(:info).with(/Task was previously processed by Worker id:.*which does not exist any more/)
+        worker.delete
+        task.log_last_worker
+      end
+
+      it "doesn't write a message if no last_worker_id in phase_context" do
+        expect(MiqWorker).not_to receive(:find_by)
+        expect($log).not_to receive(:info).with(/Task was previously processed by Worker id:/)
+        task.log_last_worker
+      end
+    end
   end
 end