@hastebrot Scopes partition the objects in an application and those partitions can carry over in the test cases. For example, if there's a scope "PaymentWindow" that builds an object graph of all things for an instance of PaymentWindow, there can be a bunch of tests that could pull in a scope-limited object graph of mocked PaymentWindow test objects.
In this case, the DI works as with a non-scoped test case. DI pulls in test implementations.
Where I see scopes relating to testing is that you might write test infrastructure to initiate a scope. In TornadoFX, an opened window might create a scope but in an automated test case, you might have to programmatically create the scope.