Merge pull request #6 from ZipCodeCore/copilot/add-unit-tests-structure

Add TDD unit tests for bank account system implementation

Author: kristofer

TESTING_GUIDE.md

@@ -0,0 +1,116 @@
+# Unit Tests Guide
+
+This project includes comprehensive unit tests to guide your implementation of the bank account system.
+
+## Test Overview
+
+The tests are organized into the following test classes:
+
+### 1. PersonTest (9 tests)
+Tests for the `Person` class which represents an individual account holder with:
+- First name, last name, email, phone number
+- Getters and setters for all properties
+
+### 2. BusinessTest (3 tests)
+Tests for the `Business` class which represents a business account holder with:
+- Business name
+- Getter and setter for business name
+
+### 3. AccountTest (10 tests)
+Tests for the abstract `Account` class which includes:
+- Account holder (Person or Business)
+- Balance management
+- Account number
+- Credit and debit operations
+- Transaction history tracking
+
+### 4. CheckingAccountTest (9 tests)
+Tests for `CheckingAccount` which extends `Account` and adds:
+- **Overdraft protection** - a boolean flag
+  - When `true`: Cannot withdraw more than the current balance
+  - When `false`: Can overdraw the account (negative balance allowed)
+
+### 5. SavingsAccountTest (11 tests)
+Tests for `SavingsAccount` which extends `Account` and includes:
+- **Interest rate** - ability to earn interest
+- **Interest application** - `applyInterest()` method that adds interest to balance
+- **Overdraft protection** - Always enabled (cannot go negative)
+
+Formula: `new balance = current balance + (current balance × interest rate)`
+
+### 6. InvestmentAccountTest (12 tests)
+Tests for `InvestmentAccount` which extends `Account` and includes:
+- **Interest rate** - typically higher than savings accounts
+- **Interest application** - `applyInterest()` method
+- **No overdraft protection** - Can go negative
+- Interest applies even to negative balances
+
+Formula: `new balance = current balance + (current balance × interest rate)`
+
+## Running the Tests
+
+To run all tests:
+```bash
+mvn test
+```
+
+To run a specific test class:
+```bash
+mvn test -Dtest=PersonTest
+mvn test -Dtest=CheckingAccountTest
+```
+
+## Implementation Strategy
+
+1. **Start with the simple classes**: Implement `Person` and `Business` first
+   - These have no dependencies on other classes
+   - Run `mvn test -Dtest=PersonTest` to verify
+
+2. **Implement the abstract Account class**: Create the base functionality
+   - Define fields for account holder, balance, account number
+   - Implement basic credit/debit operations
+   - Add transaction tracking (consider using an ArrayList)
+
+3. **Implement CheckingAccount**: Extend Account
+   - Add overdraft protection field
+   - Override `debit()` to respect overdraft protection
+
+4. **Implement SavingsAccount**: Extend Account
+   - Add interest rate field
+   - Implement `applyInterest()` method
+   - Override `debit()` to prevent overdrafts
+
+5. **Implement InvestmentAccount**: Extend Account
+   - Add interest rate field
+   - Implement `applyInterest()` method
+   - Keep default `debit()` behavior (allows overdrafts)
+
+## Test-Driven Development (TDD)
+
+The tests are written before the implementation. As you implement each class:
+
+1. Run the tests - they will fail initially
+2. Implement the minimal code to make one test pass
+3. Run the tests again
+4. Repeat until all tests pass
+
+## Expected Test Results
+
+Initially, all **53 tests will fail** because the stub implementations only have TODO comments.
+
+As you complete the implementation:
+- Person: 9 tests should pass
+- Business: 3 tests should pass
+- Account + CheckingAccount: ~19 tests should pass
+- SavingsAccount: 11 tests should pass
+- InvestmentAccount: 12 tests should pass
+
+**Goal**: All 53 tests passing ✓
+
+## Key Concepts Tested
+
+- **Encapsulation**: Getters and setters for private fields
+- **Inheritance**: Account subclasses extend the abstract Account class
+- **Polymorphism**: Account holder can be Person or Business
+- **Business logic**: Overdraft protection, interest calculation
+- **State management**: Balance updates, transaction tracking

src/main/java/io/zipcoder/Account.java

@@ -1,4 +1,47 @@
 package io.zipcoder;
 
 public abstract class Account {
+    private Object accountHolder;
+    private Double balance;
+    private String accountNumber;
+    // TODO: Add a field to track transactions
+
+    public Account(Object accountHolder, Double balance, String accountNumber) {
+        // TODO: Implement constructor
+    }
+
+    public Object getAccountHolder() {
+        // TODO: Implement getter
+        return null;
+    }
+
+    public Double getBalance() {
+        // TODO: Implement getter
+        return null;
+    }
+
+    public void setBalance(Double balance) {
+        // TODO: Implement setter
+    }
+
+    public String getAccountNumber() {
+        // TODO: Implement getter
+        return null;
+    }
+
+    public void credit(Double amount) {
+        // TODO: Implement credit method (add money to account)
+        // TODO: Record this transaction
+    }
+
+    public void debit(Double amount) {
+        // TODO: Implement debit method (remove money from account)
+        // TODO: Record this transaction
+    }
+
+    public Object getTransactions() {
+        // TODO: Implement method to return transaction history
+        return null;
+    }
 }
+

src/main/java/io/zipcoder/Business.java

@@ -0,0 +1,18 @@
+package io.zipcoder;
+
+public class Business {
+    private String businessName;
+
+    public Business(String businessName) {
+        // TODO: Implement constructor
+    }
+
+    public String getBusinessName() {
+        // TODO: Implement getter
+        return null;
+    }
+
+    public void setBusinessName(String businessName) {
+        // TODO: Implement setter
+    }
+}

src/main/java/io/zipcoder/CheckingAccount.java

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+package io.zipcoder;
+
+public class CheckingAccount extends Account {
+    private boolean overdraftProtection;
+
+    public CheckingAccount(Object accountHolder, Double balance, String accountNumber, boolean overdraftProtection) {
+        super(accountHolder, balance, accountNumber);
+        // TODO: Implement constructor
+    }
+
+    public boolean getOverdraftProtection() {
+        // TODO: Implement getter
+        return false;
+    }
+
+    public void setOverdraftProtection(boolean overdraftProtection) {
+        // TODO: Implement setter
+    }
+
+    @Override
+    public void debit(Double amount) {
+        // TODO: Implement debit method
+        // If overdraftProtection is true, don't allow balance to go negative
+        // If overdraftProtection is false, allow balance to go negative
+    }
+}

src/main/java/io/zipcoder/InvestmentAccount.java

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+package io.zipcoder;
+
+public class InvestmentAccount extends Account {
+    private Double interestRate;
+
+    public InvestmentAccount(Object accountHolder, Double balance, String accountNumber, Double interestRate) {
+        super(accountHolder, balance, accountNumber);
+        // TODO: Implement constructor
+    }
+
+    public Double getInterestRate() {
+        // TODO: Implement getter
+        return null;
+    }
+
+    public void setInterestRate(Double interestRate) {
+        // TODO: Implement setter
+    }
+
+    public void applyInterest() {
+        // TODO: Implement method to apply interest to the balance
+        // New balance = current balance + (current balance * interest rate)
+        // Note: Interest applies even to negative balances
+    }
+
+    @Override
+    public void debit(Double amount) {
+        // TODO: Implement debit method
+        // Investment accounts do NOT have overdraft protection - allow balance to go negative
+    }
+}

src/main/java/io/zipcoder/Person.java

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+package io.zipcoder;
+
+public class Person {
+    private String firstName;
+    private String lastName;
+    private String email;
+    private String phoneNumber;
+
+    public Person(String firstName, String lastName, String email, String phoneNumber) {
+        // TODO: Implement constructor
+    }
+
+    public String getFirstName() {
+        // TODO: Implement getter
+        return null;
+    }
+
+    public void setFirstName(String firstName) {
+        // TODO: Implement setter
+    }
+
+    public String getLastName() {
+        // TODO: Implement getter
+        return null;
+    }
+
+    public void setLastName(String lastName) {
+        // TODO: Implement setter
+    }
+
+    public String getEmail() {
+        // TODO: Implement getter
+        return null;
+    }
+
+    public void setEmail(String email) {
+        // TODO: Implement setter
+    }
+
+    public String getPhoneNumber() {
+        // TODO: Implement getter
+        return null;
+    }
+
+    public void setPhoneNumber(String phoneNumber) {
+        // TODO: Implement setter
+    }
+}

src/main/java/io/zipcoder/SavingsAccount.java

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+package io.zipcoder;
+
+public class SavingsAccount extends Account {
+    private Double interestRate;
+
+    public SavingsAccount(Object accountHolder, Double balance, String accountNumber, Double interestRate) {
+        super(accountHolder, balance, accountNumber);
+        // TODO: Implement constructor
+    }
+
+    public Double getInterestRate() {
+        // TODO: Implement getter
+        return null;
+    }
+
+    public void setInterestRate(Double interestRate) {
+        // TODO: Implement setter
+    }
+
+    public void applyInterest() {
+        // TODO: Implement method to apply interest to the balance
+        // New balance = current balance + (current balance * interest rate)
+    }
+
+    @Override
+    public void debit(Double amount) {
+        // TODO: Implement debit method
+        // Savings accounts have overdraft protection - don't allow balance to go negative
+    }
+}