Add unit tests for volume policy checking and DataUpload operations

[shubham-pampattiwar]

Summary

Follow-up to PR #2 - add comprehensive unit tests for the BackupPlugin functions that require kubernetes client mocking.

Functions needing test coverage

Function	Requires
checkVolumePolicies()	Mock CRClient, CoreClient, volumehelper
getFirstKubevirtPVC()	Mock CRClient, CoreClient, volumehelper
Execute() success path	Mock dynamic client for DataUpload creation
Progress()	Mock dynamic client for DataUpload status
Cancel()	Mock dynamic client
createDataUpload()	Mock dynamic client
getDataUploadByOperationID()	Mock dynamic client
updateDataUpload()	Mock dynamic client

Approach

• Use k8s.io/client-go/kubernetes/fake for CoreClient
• Use sigs.k8s.io/controller-runtime/pkg/client/fake for CRClient
• Mock volumehelper.ShouldPerformSnapshotWithBackup or test with fake configmaps
• Use the existing SetDynamicClientFunc hook for dynamic client mocking

Related

• PR Add VirtualMachine BackupItemAction plugin for kubevirt datamover #2: Add VirtualMachine BackupItemAction plugin