first failing test
woo, I can roll a dice
stage of production doesn't have a name
better failing test
simplest possible pass
refactor
product stages should have an empty item count on creation
product stages have an empty count
production units aren't received
simple failing test
make the test pass as stupidly as possible
can't produce items you ain't got
now you can't produce items you don't have
refactor
no method createSystem
define methods
first failing test for the system, no items are fed into it
tests are passing now, items can be fed in
reassurance
refactor; two tests for one thing, that's daft