Think about each operational step that is required-- then think if you had just performed that step, how would you be assured everything went well?
As an example, let's pretend you've just architected an application that should help you load some data to a backend data store (maybe a database, maybe an indexed file system, maybe something else)
- How would you be sure the data you've loaded is really there?
- How would you be sure it's *all* there?
- How do you know it's available?
- How do you know it wasn't mangled in the process of loading it?
- Can you access it from all the places you need to access it?