Solution: Bank Account Test Lifecycle

import org.junit.jupiter.api.Test;
import org.junit.jupiter.api.BeforeEach;
import static org.junit.jupiter.api.Assertions.assertEquals;
class BankAccount {
    private double balance;
    public BankAccount(double initialBalance) {
        this.balance = initialBalance;
    }
    public void deposit(double amount) {
        this.balance += amount;
    }
    public void withdraw(double amount) {
        this.balance -= amount;
    }
    public double getBalance() {
        return balance;
    }
}
public class MainTest {
    private BankAccount account;
    // Runs before EACH test method (testDeposit and testWithdraw)
    @BeforeEach
    void setUp() {
        this.account = new BankAccount(100.0);
    }
    @Test
    void testDeposit() {
        account.deposit(50.0);
        // Expect 100 + 50 = 150
        assertEquals(150.0, account.getBalance(), "Balance should be 150.0 after deposit");
    }
    @Test
    void testWithdraw() {
        account.withdraw(30.0);
        // Expect 100 - 30 = 70. Even if testDeposit ran first, 
        // @BeforeEach reset us back to 100.0 before this line.
        assertEquals(70.0, account.getBalance(), "Balance should be 70.0 after withdrawal");
    }
}