Small ports owned by their consumer

• Context: a wide interface every consumer mocks whole couples them all to every capability.
• Decision: a port is declared by the core package that uses it, with at most five methods; a capability only some adapters have is an optional interface found by type assertion.
• Consequence: a manager without a board, or an agent without questions, plugs in without stubs.
• Enforced by: TestArchitecture. See Ports and adapters.