Create Integration Test for user input to game state interaction

[amw-zero]

The most important interaction in the game is between the InputStateMachine and the GameState. The InputStateMachine parses user input, and produces command messages that the GameState uses to mutate its internal state. Right now, they are both tested independently, but there's nothing that tests the full flow: The InputStateMachine producing GameStateCommands that result in the expected GameState mutations. It would be great to have this test.