Implement test for exchange USD to PLN (pass)

src/main/kotlin/camilyed/github/io/currencyexchangeapi/application/AccountService.kt

@@ -4,7 +4,6 @@ import camilyed.github.io.currencyexchangeapi.domain.Account
 import camilyed.github.io.currencyexchangeapi.domain.AccountRepository
 import camilyed.github.io.currencyexchangeapi.domain.AccountSnapshot
 import java.math.BigDecimal
-import java.util.*
 
 class AccountService(
     private val repository: AccountRepository
@@ -27,4 +26,10 @@ class AccountService(
         account.exchangePlnToUsd(amountPln = command.amount, exchangeRate = command.exchangeRate)
         return account.toSnapshot()
     }
+
+    fun exchangeUsdToPln(command: ExchangeUsdToPlnCommand): AccountSnapshot {
+        val account = repository.find(command.accountId)!!
+        account.exchangeUsdToPln(amountUsd = command.amount, exchangeRate = command.exchangeRate)
+        return account.toSnapshot()
+    }
 }

src/main/kotlin/camilyed/github/io/currencyexchangeapi/application/ExchangeUsdToPlnCommand.kt

@@ -0,0 +1,10 @@
+package camilyed.github.io.currencyexchangeapi.application
+
+import java.math.BigDecimal
+import java.util.UUID
+
+data class ExchangeUsdToPlnCommand(
+    val accountId: UUID,
+    val amount: BigDecimal,
+    val exchangeRate: BigDecimal
+)

src/main/kotlin/camilyed/github/io/currencyexchangeapi/domain/Account.kt

@@ -25,6 +25,13 @@ class Account(
         balanceUsd = balanceUsd.add(amountUsd)
     }
 
+    fun exchangeUsdToPln(amountUsd: BigDecimal, exchangeRate: BigDecimal) {
+        require(amountUsd > BigDecimal.ZERO) { "Amount must be greater than 0" }
+        val amountPln = amountUsd.multiply(exchangeRate).setScale(2, RoundingMode.HALF_EVEN)
+        balanceUsd = balanceUsd.subtract(amountUsd)
+        balancePln = balancePln.add(amountPln)
+    }
+
     fun toSnapshot(): AccountSnapshot {
         return AccountSnapshot(
             id = id,

src/test/kotlin/camilyed/github/io/currencyexchangeapi/application/AccountServiceTest.kt

@@ -10,7 +10,9 @@ import camilyed.github.io.currencyexchangeapi.testing.assertions.hasOwner
 import camilyed.github.io.currencyexchangeapi.testing.builders.CreateAccountCommandBuilder
 import camilyed.github.io.currencyexchangeapi.testing.builders.CreateAccountCommandBuilder.Companion.anAccount
 import camilyed.github.io.currencyexchangeapi.testing.builders.ExchangePlnToUsdCommandBuilder
-import camilyed.github.io.currencyexchangeapi.testing.builders.ExchangePlnToUsdCommandBuilder.Companion.anExchange
+import camilyed.github.io.currencyexchangeapi.testing.builders.ExchangePlnToUsdCommandBuilder.Companion.anExchangeToUsd
+import camilyed.github.io.currencyexchangeapi.testing.builders.ExchangeUsdToPlnCommandBuilder
+import camilyed.github.io.currencyexchangeapi.testing.builders.ExchangeUsdToPlnCommandBuilder.Companion.anExchangeToPln
 import camilyed.github.io.currencyexchangeapi.testing.fakes.TestingAccountRepository
 import org.junit.jupiter.api.Test
 import strikt.api.expectCatching
@@ -77,7 +79,7 @@ class AccountServiceTest : SetNextAccountIdAbility, CreateAccountAbility {
 
         // when
         account = exchangePlnToUsd(
-            anExchange()
+            anExchangeToUsd()
                 .withAccountId(account.id)
                 .withAmount("400.00")
                 .withExchangeRate("4.0")
@@ -97,7 +99,7 @@ class AccountServiceTest : SetNextAccountIdAbility, CreateAccountAbility {
         // then
         expectCatching {
             exchangePlnToUsd(
-                anExchange()
+                anExchangeToUsd()
                     .withAccountId(account.id)
                     .withAmount("0.00")
             )
@@ -113,24 +115,24 @@ class AccountServiceTest : SetNextAccountIdAbility, CreateAccountAbility {
 
         // and
         account = exchangePlnToUsd(
-            anExchange()
+            anExchangeToUsd()
                 .withAccountId(account.id)
                 .withAmount("400.00")
                 .withExchangeRate("4.0")
         )
 
         // when
         account = exchangeUsdToPln(
-            anExchange()
+            anExchangeToPln()
                 .withAccountId(account.id)
                 .withAmount("100.00")
                 .withExchangeRate("4.0")
         )
 
         // then
         expectThat(account)
-            .hasBalanceInPln("1000.00") // Powrót do stanu początkowego
-            .hasBalanceInUsd("0.00")    // Saldo USD powinno być teraz zerowe
+            .hasBalanceInPln("1000.00")
+            .hasBalanceInUsd("0.00")
     }
 
     private fun create(command: CreateAccountCommandBuilder): AccountSnapshot {
@@ -140,4 +142,8 @@ class AccountServiceTest : SetNextAccountIdAbility, CreateAccountAbility {
     private fun exchangePlnToUsd(command: ExchangePlnToUsdCommandBuilder): AccountSnapshot {
         return accountService.exchangePlnToUsd(command.build())
     }
+
+    private fun exchangeUsdToPln(command: ExchangeUsdToPlnCommandBuilder): AccountSnapshot {
+        return accountService.exchangeUsdToPln(command.build())
+    }
 }

src/test/kotlin/camilyed/github/io/currencyexchangeapi/testing/builders/ExchangePlnToUsdCommandBuilder.kt

@@ -22,7 +22,7 @@ class ExchangePlnToUsdCommandBuilder private constructor() {
     }
 
     companion object {
-        fun anExchange(): ExchangePlnToUsdCommandBuilder {
+        fun anExchangeToUsd(): ExchangePlnToUsdCommandBuilder {
             return ExchangePlnToUsdCommandBuilder()
         }
     }

src/test/kotlin/camilyed/github/io/currencyexchangeapi/testing/builders/ExchangeUsdToPlnCommandBuilder.kt

@@ -0,0 +1,29 @@
+package camilyed.github.io.currencyexchangeapi.testing.builders
+
+import camilyed.github.io.currencyexchangeapi.application.ExchangeUsdToPlnCommand
+import java.math.BigDecimal
+import java.util.*
+
+class ExchangeUsdToPlnCommandBuilder private constructor() {
+    private var accountId: UUID = UUID.randomUUID()
+    private var amount: BigDecimal = BigDecimal("100.00")
+    private var exchangeRate: BigDecimal = BigDecimal("4.0")
+
+    fun withAccountId(accountId: UUID) = apply { this.accountId = accountId }
+    fun withAmount(amount: String) = apply { this.amount = BigDecimal(amount) }
+    fun withExchangeRate(exchangeRate: String) = apply { this.exchangeRate = BigDecimal(exchangeRate) }
+
+    fun build(): ExchangeUsdToPlnCommand {
+        return ExchangeUsdToPlnCommand(
+            accountId = accountId,
+            amount = amount,
+            exchangeRate = exchangeRate
+        )
+    }
+
+    companion object {
+        fun anExchangeToPln(): ExchangeUsdToPlnCommandBuilder {
+            return ExchangeUsdToPlnCommandBuilder()
+        }
+    }
+}