nYou never want to
obscure the MSS in your Use Case
nNeed it sitting there
as a guiding light
nDocument your Extension
Conditions separately
nNumbering your MSS
steps makes it easier
nExamples:
n*a. Network Goes Down
n*b. User walks away without Notice (time-out)
n1a. User enters non-multiple of $20
n2a. Insufficient funds in ATM
n4a. Bank Computer does not reply
n5a. Out of Receipt Paper