questions regarding the migration tool that we'd like clarified

[SAPProject]

Questions

What happens when we migrate a work item from Source Project that is assigned to a user that is no longer with our organisation?
What happens if we migrate work items that are required in Target Project that don't a field/ data in source project?
What happens if we migrate work items that are not required in Target Projectthat don't a field/ data in source project?
What are some other errors that can cause the migration tool to fail?

[MrHinsh]

What happens when we migrate a work item from Source Project that is assigned to a user that is no longer with our organisation?

The name becomes Text

What happens if we migrate work items that are required in Target Project that don't a field/ data in source project?

Do you mean "What happens if we migrate work items that have a required field in Target Project that don't a field/ data in the source project?"

If so, then the target field will be "illegally empty", and upon opening it, a user will be forced to fix the issue before saving.

What happens if we migrate work items that are not required in Target Projectthat don't a field/ data in source project?

Nothing.

The tool iterates through the existing fields in the source, and send them to the same field name in the target. If it does not exist then noting happens. You can modify where the data goes with field-mapps.

What are some other errors that can cause the migration tool to fail?

Many, many things. You will need to run it and see what applies to your environemnt.