AssertionFailedError error when trying to compare two objects from the same class(after Overriding Equals() and Hashcode())

Question

I tried in the first time to Override my class(Money) to check two objects on a specific attribute. a second time I tried to check two same objects from the same class(Money) but it didn't work.

I tried Overriding Equals() and Hashcode()

On the first class(Money). On the top of file.

    public static final Money HALF_DINAR = new Money(BigDecimal.valueOf(0.50));
public BigDecimal current_Money;
    public static final Money ZERO =new Money(BigDecimal.ZERO);
    public static Money mInsideMachine = new Money(BigDecimal.ZERO);

    @Override
    public boolean equals(Object o) {

        if (o == this) return true;

        if (!(o instanceof Money)) {
            return false;
        }
        Money money = (Money) o;


        return new EqualsBuilder()
                .append(this.current_Money,money.current_Money)
                .isEquals();
    }

    @Override
    /*public int hashCode() {
        return Objects.hash(current_Money);
    }*/
    public int hashCode(){
            return new HashCodeBuilder(17, 37)
                    .append(current_Money)
                    .toHashCode();
    }

The command I using to check the Objects is

 assertThat(snackMachine.moneyInside()).isEqualTo(Money.HALF_DINAR);

*Be noted: the object snackMachine is from class SnackMachine but the return is from Money's class. here is the code for moneyInside.

    public Money moneyInside() {
        return Money.mInsideMachine;
}

The Code of second file(non changable)(SnackMachine class) Unit test

 @Test
    void buying_a_snack_after_inserting_just_enough_money_then_the_money_inside_should_equals_to_money_inserted() {
        snackMachine.insertMoney(Money.QUARTER_DINAR);
        snackMachine.insertMoney(Money.QUARTER_DINAR);

        snackMachine.buySnack(SnackType.CHEWING_GUM);

        System.out.println("Moneyinside (Unit test)"+Money.mInsideMachine.current_Money.toString());
        System.out.println("Money half dinar (Unit test)"+Money.HALF_DINAR.current_Money.toString());
        //assertThat(snackMachine.moneyInTransaction()).isEqualTo(Money.ZERO);
        assertThat(snackMachine.moneyInside()).isEqualTo(Money.HALF_DINAR);

    }

I added some code to print the values and the output is:

Moneyinside (Unit test)0.50
Money half dinar (Unit test)0.5


org.opentest4j.AssertionFailedError: 
Expecting:
 <com.progressoft.induction.Money@885>
to be equal to:
 <com.progressoft.induction.Money@311>
but was not.
Expected :com.progressoft.induction.Money@311
Actual   :com.progressoft.induction.Money@885

Answer 1

The issue here is that 0.5 is not equal to 0.50 unless you use isEqualByComparingTo . see https://docs.oracle.com/javase/8/docs/api/java/math/BigDecimal.html#compareTo-java.math.BigDecimal-

example:

 // assertion will pass because 8.0 is equal to 8.00 using BigDecimal.compareTo(BigDecimal)
 assertThat(new BigDecimal("8.0")).isEqualByComparingTo(new BigDecimal("8.00"));
 // assertion fails 
 assertThat(new BigDecimal("8.0")).isEqualTo(new BigDecimal("8.00"));