bank-test.kt

val bank1 = Bank()
val memimg1 = MemImg(bank1, eventSourcing)
​
memimg1.execute(CreateAccount("janet", "Janet Doe"))
assertEquals(Amount.ZERO, bank1.accounts["janet"]!!.balance)
​
memimg1.execute(Deposit("janet", Amount(100)))
assertEquals(Amount(100), bank1.accounts["janet"]!!.balance)
​
memimg1.execute(Withdrawal("janet", Amount(10)))
assertEquals(Amount(90), bank1.accounts["janet"]!!.balance)
​
memimg1.execute(CreateAccount("john", "John Doe"))
assertEquals(Amount.ZERO, bank1.accounts["john"]!!.balance)
​
memimg1.execute(Deposit("john", Amount(50)))
assertEquals(Amount(50), bank1.accounts["john"]!!.balance)
​
memimg1.execute(Transfer("janet", "john", Amount(20)))
assertEquals(Amount(70), bank1.accounts["janet"]!!.balance)
assertEquals(Amount(70), bank1.accounts["john"]!!.balance)
​
memimg1.close()
​
val bank2 = Bank()
val memimg2 = MemImg(bank2, eventSourcing)
// System state restored from empty state via event sourcing!
assertEquals(Amount(70), bank2.accounts["janet"]!!.balance)
assertEquals(Amount(70), bank2.accounts["john"]!!.balance)
​
// Some random query; executes at in-memory speeds
val accountsWith70 = memimg2.execute(object : BankQuery {
    override fun extractFrom(bank: Bank) =
        bank.accounts.values
            .filter { it.balance == Amount(70) }
            .map { it.name }
            .toSet()
})
assertEquals(setOf("Janet Doe", "John Doe"), accountsWith70)
​
// Attempt to transfer beyond means...
val insufficientFunds = assertThrows<CommandApplicationException> {
    memimg2.execute(Transfer("janet", "john", Amount(1000)))
}
assertContains(insufficientFunds.message!!, "Invalid value for Account.balance")
// Look ma: system state restored on failure after partial mutation
assertEquals(Amount(70), bank2.accounts["janet"]!!.balance)
assertEquals(Amount(70), bank2.accounts["john"]!!.balance)
​
memimg2.close()