Java Banking System JUnit Tests: Comprehensive Testing for Account Management

Comprehensive Java JUnit Tests for Banking System Functionality

In this Java code snippet, a robust set of JUnit tests has been meticulously crafted to thoroughly assess the functionality of a banking system. These tests cover critical aspects such as account creation, balance initialization, APR setting, depositing, and withdrawing, ensuring the system's correctness and reliability. The detailed breakdown of the code serves as a valuable resource for developers seeking to understand and enhance their Java programming skills, particularly in the context of building and testing financial systems. Whether you're a student grappling with a Java assignment or a developer seeking to fortify your understanding of Java testing methodologies, this comprehensive example provides insights that can help with your Java assignment and further advance your programming proficiency.

Block 1: Imports

import java.util.*;
import org.junit.*;
import static org.junit.Assert.*;

Discussion:

The code starts with importing necessary Java libraries.
java.util.* is imported to use utility classes like List.
org.junit.* is imported for JUnit testing framework.
static org.junit.Assert.* is imported to use static methods for assertions.

Block 2: BankTest Class Declaration

public class BankTest {
private Bank bank = new Bank();

Discussion:

The BankTest class is declared, which is used for testing the banking functionality.
An instance of the Bank class is created as a private member variable named bank.

Block 3: Test for CheckingAccount Balance Initialization

@Test
public void checkingAccount_balanceIsZero() {
CheckingAccount account = new CheckingAccount(12345678, 0);
assertEquals(0, account.getBalance(), 0.001);
}

Discussion:

A JUnit test method is defined to check if the balance of a checking account is initialized to zero.
An instance of CheckingAccount is created with an account number and initial balance of zero.
The assertEquals method is used to verify that the account's balance is indeed zero.

Block 4: Test for SavingsAccount Balance Initialization

@Test
public void savingsAccount_balanceIsZero() {
SavingsAccount account = new SavingsAccount(23456789, 2);
assertEquals(0, account.getBalance(), 0.001);
}

Discussion:

A similar JUnit test is defined for a savings account to ensure its balance is initialized to zero.
An instance of SavingsAccount is created with an account number and an APR value.
The assertEquals method is used to validate the initial balance.

Block 5: Test for CertificateOfDeposit Balance Initialization

@Test
public void cdAccount_balanceIsSuppliedBalance() {
CertificateOfDeposit account = new CertificateOfDeposit(34567890, 3, 1000);
assertEquals(1000, account.getBalance(), 0.001);
}

Discussion:

This test checks whether the balance of a Certificate of Deposit (CD) account is set to the supplied balance.
An instance of CertificateOfDeposit is created with an account number, APR value, and an initial balance.
The assertEquals method is used to verify the balance.

Block 6: Test for APR Initialization in All Accounts

@Test
public void account_aprIsSuppliedApr() {
Account account = new CheckingAccount(10000000, 5);
assertEquals(5, account.getApr(), 0.001);
}

Discussion:

This test ensures that the APR of an account is set to the supplied APR value.
An instance of a generic Account is created (using a CheckingAccount for testing purposes) with an account number and APR value.
The assertEquals method is used to confirm that the APR is set correctly.

Block 7: Test for Deposit Functionality in All Accounts

@Test
public void deposit_validAmount_balanceIncreases() {
Account account = new CheckingAccount(12345678, 0);
account.deposit(100);
assertEquals(100, account.getBalance(), 0.001);
}

Discussion:

This test checks whether depositing into an account increases its balance.
An instance of an account is created with an initial balance of zero.
The deposit method is called to add 100 to the account.
The assertEquals method is used to verify that the balance has increased to 100.

Block 8: Test for Withdrawal Functionality in All Accounts

@Test
public void withdraw_validAmount_balanceDecreases() {
Account account = new CheckingAccount(12468035, 0);
account.deposit(100);
account.withdraw(50);
assertEquals(50, account.getBalance(), 0.001);
}

Discussion:

This test ensures that withdrawing from an account decreases its balance.
An instance of an account is created with an initial balance of zero.
The deposit method is used to add 100 to the account, and then withdraw is called to remove 50.
The assertEquals method verifies that the balance is now 50.

Block 9: Test for Withdrawal Limit in All Accounts

@Test
public void withdraw_excessiveAmount_balanceIsZero() {
Account account = new CheckingAccount(12345678, 0);
account.deposit(100);
account.withdraw(200);
assertEquals(0, account.getBalance(), 0.001);
}

Discussion:

This test ensures that withdrawing an excessive amount results in the account balance being set to zero.
An instance of an account is created with an initial balance of zero, 100 is deposited, and then 200 is withdrawn.
The assertEquals method confirms that the balance is zero.

Block 10: Test for Multiple Deposits in All Accounts

@Test
public void depositTwice_validAmounts_balanceIncreases() {
Account account = new CheckingAccount(12345678, 0);
account.deposit(100);
account.deposit(50);
assertEquals(150, account.getBalance(), 0.001);
}

Discussion:

This test ensures that depositing twice into the same account works as expected.
An instance of an account is created with an initial balance of zero.
Two deposits are made, and the assertEquals method verifies that the balance is now 150.

Block 11: Test for Multiple Withdrawals in All Accounts

@Test
public void withdrawTwice_validAmounts_balanceDecreases() {
Account account = new CheckingAccount(10000000, 0);
account.deposit(100);
account.withdraw(50);
account.withdraw(30);
assertEquals(20, account.getBalance(), 0.001);
}

Discussion:

This test ensures that withdrawing twice from the same account works as expected.
An instance of an account is created with an initial balance of zero.
A deposit is made, followed by two withdrawals, and the assertEquals method confirms the final balance.

Block 12: Test for Initial Bank State

@Test
public void bank_initiallyHasNoAccounts() {
assertEquals(0, bank.getAccounts().size());
}

Discussion:

This test checks whether a newly created Bank has no accounts initially.
The assertEquals method verifies that the size of the accounts list in the bank is zero.

Block 13: Test for Adding One Account to the Bank

@Test
public void addAccount_bankHasOneAccount() {
bank.addAccount(new CheckingAccount(11111111, 0));
assertEquals(1, bank.getAccounts().size());
}

Discussion:

This test ensures that adding one account to the bank results in the bank having one account.
A new checking account is created and added to the bank.
The assertEquals method confirms that the size of the accounts list in the bank is one.

Block 14: Test for Adding Two Accounts to the Bank

@Test
public void addTwoAccounts_bankHasTwoAccounts() {
bank.addAccount(new CheckingAccount(12345678, 0));
bank.addAccount(new SavingsAccount(23456789, 2));
assertEquals(2, bank.getAccounts().size());
}

Discussion:

This test ensures that adding two accounts to the bank results in the bank having two accounts.
A checking account and a savings account are created and added to the bank.
The assertEquals method confirms that the size of the accounts list in the bank is two.

Block 15: Test for Retrieving an Account from the Bank

@Test
public void getAccount_validId_returnsCorrectAccount() {
CheckingAccount account1 = new CheckingAccount(10000000, 0);
bank.addAccount(account1);
assertEquals(account1, bank.getAccount(10000000));
}

Discussion:

This test checks whether retrieving an account from the bank using a valid ID returns the correct account.
A checking account is created, added to the bank, and then retrieved using the account number.
The assertEquals method confirms that the retrieved account is the same as the one added.

Block 16: Test for Deposit Through the Bank

@Test
public void deposit_validId_correctAccountBalanceIncreases() {
CheckingAccount account = new CheckingAccount(10000000, 0);
bank.addAccount(account);
bank.deposit(10000000, 100);
assertEquals(100, account.getBalance(), 0.001);
}

Discussion:

This test ensures that depositing money by ID through the bank results in the correct account's balance increasing.
A checking account is created, added to the bank, and then a deposit is made through the bank.
The assertEquals method confirms that the account's balance has increased.

Block 17: Test for Withdrawal Through the Bank

@Test
public void withdraw_validId_correctAccountBalanceDecreases() {
CheckingAccount account = new CheckingAccount(12345678, 0);
bank.addAccount(account);
account.deposit(100);
bank.withdraw(12345678, 50);
assertEquals(50, account.getBalance(), 0.001);
}

Discussion:

This test ensures that withdrawing money by ID through the bank results in the correct account's balance decreasing.
A checking account is created, added to the bank, and then a deposit is made directly to the account.
A withdrawal is then made through the bank, and the assertEquals method confirms the account's balance.

Block 18: Test for Multiple Deposits Through the Bank

@Test
public void depositTwiceThroughBank_validAmounts_balanceIncreases() {
CheckingAccount account = new CheckingAccount(11111111, 0);
bank.addAccount(account);
bank.deposit(11111111, 100);
bank.deposit(11111111, 50);
assertEquals(150, account.getBalance(), 0.001);
}

Discussion:

This test ensures that depositing twice through the bank into the same account works as expected.
A checking account is created, added to the bank, and then two deposits are made through the bank.
The assertEquals method confirms that the account's balance is now 150.

Block 19: Test for Multiple Withdrawals Through the Bank

@Test
public void withdrawTwiceThroughBank_validAmounts_balanceDecreases() {
CheckingAccount account = new CheckingAccount(10000000, 0);
bank.addAccount(account);
account.deposit(100);
bank.withdraw(10000000, 50);
bank.withdraw(10000000, 30);
assertEquals(20, account.getBalance(), 0.001);
}

Discussion:

This test ensures that withdrawing twice through the bank from the same account works as expected.
A checking account is created, added to the bank, and then a deposit is made directly to the account.
Two withdrawals are then made through the bank, and the assertEquals method confirms the account's balance.

Conclusion

In conclusion, these Java JUnit tests stand as a testament to meticulous software testing practices, ensuring the robustness and reliability of a banking system's core functionalities. This code snippet serves as a valuable educational resource for developers, offering insights into Java programming, testing methodologies, and financial system development. Whether you are a student working on a Java assignment or a seasoned developer aiming to refine your skills, the provided example can guide you in mastering intricate aspects of Java programming. Embrace these comprehensive tests to enhance your proficiency and contribute to the creation of secure and efficient banking software solutions.