Property can be set to the NodePath of a Terminal node. Doing so will
conveniently set up the neccessary signals between Terminal and PTY for
them to function together.
Adds additional tests for the interface. Creates a new base test class
GodotXtermTest that adds some additional assert methods. Tests
inheriting from this should override the got_described_class() method.
Add instance of the described class named 'subject' will be created and
added to the scene tree before each test.
