sandromancuso

@RunWith(MockitoJUnitRunner.class)
public class VoucherDiscountCalculationTest {

    private static final String NO_VOUCHER = null;
    private static final String TWENTY_POUNDS_VOUCHER = "20";

    @Mock
    private VoucherService voucherService;
    private VoucherDiscountCalculation voucherDiscountCalculation;

sandromancuso

@RunWith(MockitoJUnitRunner.class)
public class VoucherPricingServiceTest {

    private static final User UNUSED_USER = null;
    private static final String NO_VOUCHER = null;
    private static final String TWENTY_POUNDS_VOUCHER = "20";
    
    @Mock private VoucherService voucherService;
    private TestableVoucherPricingService voucherPricingService;

sandromancuso

public class VoucherService {
    public double getVoucherValue(String voucher) {
        // Imagine that this calculate the voucher price.
        // Keeping it simple so we can understand the approach.
        return 0;
    }
}

sandromancuso

public class VoucherPricingService extends UserDiscountPricingService {

    private VoucherService voucherService;

    @Override
    protected double applyAdditionalDiscounts(double total, User user, String voucher) {
        double voucherValue = voucherService.getVoucherValue(voucher);
        double totalAfterValue = total - voucherValue;
        return (totalAfterValue > 0) ? totalAfterValue : 0;
    }

sandromancuso

public class ShoppingBasketBuilder {

    private Map<Product, Integer> products = new HashMap<Product, Integer>();

    public static ShoppingBasketBuilder aShoppingBasket() {
        return new ShoppingBasketBuilder();
    }
    
    public ShoppingBasketBuilder with(Product product) {
        this.products.put(product, 1);

sandromancuso

public class ProductBuilder {
    
    private double price;
    private String name;
    
    public static ProductBuilder aProduct() {
        return new ProductBuilder();
    }
    
    public ProductBuilder costing (double price) {

sandromancuso

@RunWith(MockitoJUnitRunner.class)
public class PricingServiceTest {

    private static final String NO_VOUCHER = "";

    private TestablePricingService pricingService = new TestablePricingService();
    private ShoppingBasket shoppingBasket;
    
    @Mock private PriceCalculation priceCalculation;
    

sandromancuso

public abstract class PricingService {

    private PriceCalculation priceCalculation;

    public double calculatePrice(ShoppingBasket shoppingBasket, User user, String voucher) {
        double discount = calculateDiscount(user);
        double total = 0;
        for (ShoppingBasket.Item item : shoppingBasket.items()) {
            total += priceCalculation.calculateProductPrice(item.getProduct(), item.getQuantity());
        }

sandromancuso

public interface PriceCalculation {
    double calculateProductPrice(Product product, int quantity);
}

public class BoxingDayPriceCalculation implements PriceCalculation 

public class StandardPriceCalculation implements PriceCalculation 

sandromancuso

public class BoxingDayPriceCalculationTest {
    
    private BoxingDayPriceCalculation priceCalculation = new BoxingDayPriceCalculation();

    @Test public void
    should_apply_boxing_day_discount_on_product_price() {
        Product book = aProduct().costing(10).build();

        double price = priceCalculation.calculateProductPrice(book, 1);