@Kien I want to be helpful, but your workflow question is extremely vague. There is a lot you can do with a workflow, and a few ways to test. If it is a scheduled workflow, but the WF in testing status and execute the workflow. It will run for a small subset of affected records. If you are testing an action on a form or something like that, leave the workflow in a Released state and see if the workflow does what you set out to make it do...