Hopefully will display better on pub now.

Will allow the interface between the testable and untestable code to be
defined without altering the external handling.

Still don't have good way to test impl without pulling it in.

Can change it for testing. Does seem a bit excessive at this point.

For tests must be sure that the variables don't carry over if they have
different behaviours configured.

Allows for testing to use mock versions

Verifies that the interactions can be mocked enough to implement tests.

Since the stream is handled by the Many object created, it is difficult
to wrap that well.