Meet Bella. She will destroy your documents.
Register a fake cursor so user can safely interact with Bella
Allow multiple instances of Bella
Show Bella how to exercise the entire selection API
Teach Bella how to meow (and other text manipulation actions)
Try and make the average selection range smaller
Using a real SessionController causes problems with double-events
Teach Bella about undo & redo
Now Bella will also destroy your document formatting too!
Learn about cut, copy & paste
Give Bella some sugar
Discovered Bella is a tidy cat and likes valid documents

Ensure known bad conditions aren't encountered during modifications.
E.g., look for occurrences of empty spans (issue #37).
Add more spaces when inserting text

Spaces increase the number of nodes in the document significantly and
tend to cause a lot of issues range selections and positions.
Control the undo stack size during play
Check document validity after each operation

Makes diagnosis of problems easier to detect
Make Bella less likely to delete the entire document
Add workaround for crashing TrivialUndoManager bug

TODO - raise an issue about this!