Wow领域模型即服务

fun onCommand(command: Withdraw): Withdrawn {
    if (command.amount > state.balance) {
        reject(Rejections.INSUFFICIENT_BALANCE, "The balance is ${state.balance}.")
    }
    return Withdrawn(command.amount)
}

@Test
fun `a withdrawal the balance does not cover is rejected`() = aggregateSpec(model, id = "alice") {
    given(AccountOpened("Alice"), Deposited(100))
    whenCommand(Withdraw(150)) { expectRejected(Account.Rejections.INSUFFICIENT_BALANCE) }
    whenCommand(Withdraw(30)) {
        expectEvents(Withdrawn(30))
        expectState { balance.assert().isEqualTo(70) }
    }
}