successful test

src/main/java/guru/springframework/Bank.java

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+package guru.springframework;
+
+public class Bank {
+
+    Money reduce(Expression expr, String currency){
+        return expr.reduce(currency);
+//        if (expr instanceof Money) return (Money) expr;
+//        Sum expressionCasted= (Sum) expr;
+//        return expressionCasted.reduce(currency);
+    }
+}

src/main/java/guru/springframework/Expression.java

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+package guru.springframework;
+
+public interface Expression {
+    Money reduce(String to);
+}

src/main/java/guru/springframework/Money.java

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+package guru.springframework;
+
+public class Money implements Expression {
+
+    protected int amount;
+    protected String currency;
+
+    public Money(int amount,String currency) {
+        this.amount=amount;
+        this.currency=currency;
+    }
+
+    protected String currency(){
+        return currency;
+    };
+
+    public boolean equals(Object object){
+        Money testObject =(Money) object;
+        return testObject.amount == amount
+                && currency==testObject.currency;
+    }
+
+    public Money times(int multiplyBy) {
+        return new Money(amount * multiplyBy,currency);
+
+    }
+
+    public static Money dollar(int amount){
+        return new Money(amount, "USD") {
+        };
+    }
+
+    public static Money franc(int amount){
+        return new Money(amount, "CHF") {
+        };
+    }
+
+    public Expression plus(Money addend){
+        return new Sum(this,addend);
+    }
+
+    @Override
+    public Money reduce(String to){
+        return this;
+    }
+
+    @Override
+    public String toString() {
+        return "Money{" +
+                "amount=" + amount +
+                ", currency='" + currency + '\'' +
+                '}';
+    }
+}

src/main/java/guru/springframework/Sum.java

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+package guru.springframework;
+
+import java.util.Currency;
+
+public class Sum implements Expression {
+    Money augmend;
+    Money addmend;
+
+    public Sum(Money augmend, Money addmend) {
+        this.augmend = augmend;
+        this.addmend = addmend;
+    }
+
+    public Money reduce(String curr){
+        return new Money(augmend.amount + addmend.amount, curr);
+    }
+}

src/test/java/guru/springframework/MoneyTest.java

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+package guru.springframework;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNotEquals;
+
+public class MoneyTest {
+    @Test
+    void testMultiplication(){
+        Money five= Money.dollar(5);
+        assertEquals(Money.dollar(10), five.times(2));
+        assertEquals(Money.dollar(15), five.times(3));
+
+        Money fivef= Money.franc(5);
+        assertEquals(Money.franc(10), fivef.times(2));
+        assertEquals(Money.franc(15), fivef.times(3));
+    }
+
+    @Test
+    void testEqualityFranc(){
+        assertEquals(false,Money.franc(1).equals(Money.franc(2)));
+        assertEquals(true,Money.franc(1).equals(Money.franc(1)));
+    }
+
+    @Test
+    void testCurrency(){
+        assertEquals("USD",Money.dollar(1).currency());
+        assertEquals("CHF",Money.franc(1).currency());
+    }
+
+    @Test
+    void testAddition(){
+        Money five=Money.dollar(5);
+        Expression result=five.plus(five);
+        Sum sum=(Sum) result;
+        assertEquals(five, sum.addmend);
+        assertEquals(five, sum.augmend);
+    }
+
+    @Test
+    void testReduceSum(){
+        Expression sum =new Sum(Money.dollar(3),Money.dollar(4));
+        Bank bank =new Bank();
+        Money result=bank.reduce(sum,"USD");
+        assertEquals(Money.dollar(7),result);
+
+    }
+
+    @Test
+    void testReduceMoney(){
+        Bank bank=new Bank();
+        Money result=bank.reduce(Money.dollar(1),"USD");
+        assertEquals(Money.dollar(1),result);
+
+    }
+
+
+
+}