Testing and using flows is much like testing and using forms . Please refer to the forms chapter for the bulk of information on this topic. We'll only discuss the differences here
Testing Flows
When you click Test icon will display your flow in “Use Mode”—in other words, the flow will appear and behave exactly as it will when users access it. To test the flow, just complete it as your users would and click Submit. Test mode allows you to view your flow as it would appear on a desktop, iPad or iPhone. Refer to Testing Forms for more information about Test Mode views.
The Flow Tutorial is a fabulous way to learn how to test your flows.
Approving a Flow Task
Rejecting a Flow Task
Notification Email
There are many places that generate emails: task notification, activity document action, anonymous client activities, form action, escalation reminders.