Add test coverage to new code added fr IaaS-native disk resize

Author: bgandon

src/bosh-director/lib/bosh/director/deployment_plan/persistent_disk_collection.rb

@@ -147,8 +147,7 @@ def size_diff_only?(other)
 
         def is_bigger_than?(other)
           unless other.is_a? PersistentDisk
-            raise Exception, 'Cannot compare persistent disk size to anything
-                              that is not a persistent disk.'
+            raise Exception, 'Cannot compare persistent disk size to anything that is not a persistent disk.'
           end
 
           size >= other.size

src/bosh-director/spec/unit/deployment_plan/persistent_disk_collection_spec.rb

@@ -349,6 +349,44 @@ module DeploymentPlan
           end
         end
       end
+
+      describe '#is_bigger_than?' do
+        let(:new_disk) { new_disk = PersistentDiskCollection::PersistentDisk.new('', {}, 10) }
+
+        context 'when other thing is not a disk' do
+          it 'raises an error' do
+            old_disk = {}
+
+            expect {
+              new_disk.is_bigger_than?(old_disk)
+            }.to raise_error(/Cannot compare persistent disk size to anything that is not a persistent disk/)
+          end
+        end
+
+        context 'when the size is bigger' do
+          it 'is true' do
+            old_disk = PersistentDiskCollection::PersistentDisk.new('', {}, 5)
+
+            expect(new_disk.is_bigger_than?(old_disk)).to eq(true)
+          end
+        end
+
+        context 'when the size is equal' do
+          it 'is true' do
+            old_disk = PersistentDiskCollection::PersistentDisk.new('', {}, 10)
+
+            expect(new_disk.is_bigger_than?(old_disk)).to eq(true)
+          end
+        end
+
+        context 'when the size is smaller' do
+          it 'is false' do
+            old_disk = PersistentDiskCollection::PersistentDisk.new('', {}, 15)
+
+            expect(new_disk.is_bigger_than?(old_disk)).to eq(false)
+          end
+        end
+      end
     end
   end
 end

src/bosh-director/spec/unit/disk_manager_spec.rb

@@ -239,7 +239,7 @@ module Bosh::Director
         end
 
         context 'when resize_disk is not supported' do
-          let(:job_persistent_disk_size) { 512 }
+          let(:job_persistent_disk_size) { 3072 }
 
           it 'falls back to manually copying disk' do
             allow(cloud).to receive(:resize_disk).and_raise(Bosh::Clouds::NotSupported)
@@ -248,11 +248,24 @@ module Bosh::Director
 
             expect(cloud).to have_received(:detach_disk).with('vm234', 'disk123').twice
             expect(cloud).to have_received(:resize_disk)
-            expect(cloud).to have_received(:create_disk).with(512, { 'cloud' => 'properties' }, 'vm234')
+            expect(cloud).to have_received(:create_disk).with(3072, { 'cloud' => 'properties' }, 'vm234')
             expect(cloud).to have_received(:attach_disk).with('vm234', 'disk123')
             expect(cloud).to have_received(:attach_disk).with('vm234', 'new-disk-cid')
           end
         end
+
+        context 'when shrinking disk' do
+          let(:job_persistent_disk_size) { 512 }
+
+          it 'falls back to manually copying disk' do
+            disk_manager.update_persistent_disk(instance_plan)
+
+            expect(cloud).not_to have_received(:resize_disk)
+            expect(cloud).to have_received(:create_disk).with(512, { 'cloud' => 'properties' }, 'vm234')
+            expect(cloud).to have_received(:attach_disk).with('vm234', 'new-disk-cid')
+            expect(cloud).to have_received(:detach_disk).with('vm234', 'disk123')
+          end
+        end
       end
 
       context 'when disk creation fails' do