add tests [easy]
add tests [easy]

Summary:
Very minimal CFGInliner test.
Bonus test for needs_receiver_cast behavior.

Reviewed By: beicy

Differential Revision: D31978669

fbshipit-source-id: 86e8b9a7ab34dcd534f490ad779df78b7719dfd3

facebook/redex,facebook/redex,facebook/redex,facebook/redex,facebook/redex,facebook/redex,facebook/redex,facebook/redex,facebook/redex