Accepting conditions
An accepting condition marks which states are goal (or "complete") states. A
state is accepting when all accepting conditions return true in that state.
[AcceptingCondition]
public bool AllDelivered() =>
Users.All(u => u.Inbox.Count == 0);
An accepting condition is a parameterless bool method marked
[AcceptingCondition]. You may declare several; the state is accepting only if
every one holds.
Why they matter
Accepting states are the targets for constructing complete behaviors:
construct accepting paths for <machine>keeps only paths that end in an accepting state.construct test cases for <machine>derives tests whose runs end in accepting states.
In model-based testing terms, accepting states usually encode "the protocol run finished cleanly" or "the acceptance criterion is satisfied". Reaching one during exploration is evidence that the corresponding behavior is achievable.
Important
If a model declares no accepting conditions, then no state is accepting.
Give your model at least one accepting condition (even => true) if you want
every state to count as a valid stopping point.
Examples from the samples
- SMB2: accepting when the session is torn down —
!SessionUp && Trees.Count == 0— i.e. a full connect → work → disconnect run completed. - chat: accepting when the protocol is quiescent — everyone logged on and no broadcasts pending acknowledgement.
- Sailboat: accepting at the initial position (
X == 0 && Y == 0), modeling a completed there-and-back voyage.
Relationship to guards
Guards decide when an action can happen; accepting conditions decide when a state is a valid goal. They are independent: a state can be accepting yet still have enabled actions leading elsewhere (e.g., you can keep going after a clean stop).