MockPaymentGateway mockup

MockPaymentGateway.java

import java.util.HashMap;
import java.util.Map;

public class PaymentProcessingService {

    // Enum for Transaction Types
    public enum TransactionType {
        CREDIT_CARD,
        BANK_TRANSFER,
        DIGITAL_WALLET
    }

    // Process Payment Method
    public String processPayment(TransactionType type, String accountId, double amount) {
        if (amount <= 0) {
            return "Invalid payment amount.";
        }

        // Basic Authentication Check
        if (!authenticateUser(accountId)) {
            return "Authentication failed.";
        }

        switch (type) {
            case CREDIT_CARD:
                return handleCreditCardPayment(accountId, amount);
            case BANK_TRANSFER:
                return handleBankTransfer(accountId, amount);
            case DIGITAL_WALLET:
                return handleDigitalWalletPayment(accountId, amount);
            default:
                return "Unsupported transaction type.";
        }
    }

    // Mock Authentication
    private boolean authenticateUser(String accountId) {
        // Simulated check for account validity
        return accountId != null && accountId.matches("\\w+");
    }

    // Handle Credit Card Payment
    private String handleCreditCardPayment(String accountId, double amount) {
        // Mock API integration
        String response = MockPaymentGateway.process("CREDIT_CARD", accountId, amount);
        return response != null ? "Credit card payment successful: " + response : "Payment failed.";
    }

    // Handle Bank Transfer
    private String handleBankTransfer(String accountId, double amount) {
        // Mock API integration
        String response = MockPaymentGateway.process("BANK_TRANSFER", accountId, amount);
        return response != null ? "Bank transfer successful: " + response : "Payment failed.";
    }

    // Handle Digital Wallet Payment
    private String handleDigitalWalletPayment(String accountId, double amount) {
        // Mock API integration
        String response = MockPaymentGateway.process("DIGITAL_WALLET", accountId, amount);
        return response != null ? "Digital wallet payment successful: " + response : "Payment failed.";
    }

    public static void main(String[] args) {
        PaymentProcessingService service = new PaymentProcessingService();
        System.out.println(service.processPayment(TransactionType.CREDIT_CARD, "user123", 150.00));
        System.out.println(service.processPayment(TransactionType.BANK_TRANSFER, "user456", 250.00));
        System.out.println(service.processPayment(TransactionType.DIGITAL_WALLET, "user789", 75.50));
    }
}

// Mock Payment Gateway
class MockPaymentGateway {
    public static String process(String paymentType, String accountId, double amount) {
        // Simulate successful response from payment gateway
        return "Transaction ID: TXN-" + Math.random() * 10000;
    }
}

PaymentProcessingServiceTest.java

// Test class for PaymentProcessingService
import org.junit.jupiter.api.Test;
import static org.junit.jupiter.api.Assertions.*;

public class PaymentProcessingServiceTest {

    @Test
    public void testCreditCardPayment() {
        PaymentProcessor service = new PaymentProcessingService();
        String result = service.process(PaymentProcessingService.TransactionType.CREDIT_CARD, "user123", 150.00);
        assertTrue(result.contains("Credit card payment successful"));
    }

    @Test
    public void testBankTransferPayment() {
        PaymentProcessor service = new PaymentProcessingService();
        String result = service.process(PaymentProcessingService.TransactionType.BANK_TRANSFER, "user456", 250.00);
        assertTrue(result.contains("Bank transfer successful"));
    }

    @Test
    public void testDigitalWalletPayment() {
        PaymentProcessor service = new PaymentProcessingService();
        String result = service.process(PaymentProcessingService.TransactionType.DIGITAL_WALLET, "user789", 75.50);
        assertTrue(result.contains("Digital wallet payment successful"));
    }

    @Test
    public void testInvalidAmount() {
        PaymentProcessor service = new PaymentProcessingService();
        String result = service.process(PaymentProcessingService.TransactionType.CREDIT_CARD, "user123", -50.00);
        assertEquals("Invalid payment amount.", result);
    }

    @Test
    public void testAuthenticationFailure() {
        PaymentProcessor service = new PaymentProcessingService();
        String result = service.process(PaymentProcessingService.TransactionType.CREDIT_CARD, "", 150.00);
        assertEquals("Authentication failed.", result);
    }
}