下面通过一个简单的测试驱动示例，并经过重构完成设计的更改。详细的例子见重构。

影片出租店的程序，计算每一位顾客的消费金额并打印报表。操作者告诉程序：顾客租用了哪些影片，租期多长，程序根据租赁时间和影片类型（普通片，儿童片和新片）。除了计算费用，还要为常客计算点数，点数的计算会由于租片种类是否为新片而有所不同。

根据上述描述，我们画出简单的类图

其中影片和租借都是简单的纯数据类。

package chapter01;

public class Movie {

       public static final int CHILDRENS=2;// 影片类型

       public static final int REGULAR=1;

       public static final int NEW_RELEASE=0;

       private String title;// 名称

       private int priceCode;// 价格代码

       public Movie(String title, int priceCode) {

              this.title = title;

              this.priceCode = priceCode;

       }

       public int getPriceCode() {

              return priceCode;

       }

       public void setPriceCode(int priceCode) {

              this.priceCode = priceCode;

       }

       public String getTitle() {

              return title;

       }

       }

public class Rental {

       private Movie movie;

       private int dayRented;

       public Rental(Movie movie, int dayRented) {

              this.movie = movie;

              this.dayRented = dayRented;

       }

       public int getDayRented() {

              return dayRented;

       }

       public Movie getMovie() {

              return movie;

       }

}

public class Customer {

       private String name;

       private Vector rentals=new Vector();

       public Customer(String name) {

              this.name = name;

       }

       public String getName() {

              return name;

       }

       public Vector getRentals() {

              return rentals;

       }

       @SuppressWarnings("unchecked")

       public void addRental(Rental rental){

              rentals.add(rental);

       }

       public String statement(){// 计算费用

              double totalAmount=0;// 总和

              int frequentCount=0;// 常客积点

              Enumeration rental=rentals.elements();

              String result="rental record for "+getName()+"\n";

              while (rental.hasMoreElements()) {

                     Rental each = (Rental) rental.nextElement();// 取得一批租借记录

                     double thisAmount=0;

                     // 根据类型，计算价格

                     switch (each.getMovie().getPriceCode()) {

                     case Movie.REGULAR:

                            thisAmount+=2;

                            if(each.getDayRented()>2)

                                   thisAmount+=(each.getDayRented()-2)*1.5;

                            break;

                     case Movie.CHILDRENS:

                            thisAmount+=1.5;

                            if(each.getDayRented()>3)

                                   thisAmount+=(each.getDayRented()-3)*1.5;

                            break;

                     case Movie.NEW_RELEASE:

                            thisAmount+=(each.getDayRented())*3;

                            break;

                     }

                     // 添加常客积点

                     frequentCount++;

                     if (each.getMovie().getPriceCode()==Movie.NEW_RELEASE&&each.getDayRented()>1)

                            frequentCount++;

                     // 显示此笔数据

                     result+=

                            "\t"+each.getMovie().getTitle()+

                            "\t"+String.valueOf(frequentCount)+"\n";

                     totalAmount+=thisAmount;

              }

              // 打印结尾

              result+="amount owned "+String.valueOf(totalAmount)+"\n";

              result+="you earned "+String.valueOf(frequentCount)+"frequentCount\n";

              return result;

       }

}

下面是对应的测试用例

public class testCustomerStatement extends TestCase {

       Movie childrenMovie=new Movie("HARRY POTTY",Movie.CHILDRENS);

       Movie regularMovie=new Movie("Titanic",Movie.REGULAR);

       Movie newMovie=new Movie("Ice Age 2",Movie.NEW_RELEASE);

       Rental childRental=new Rental(childrenMovie,3);

       Rental newRental=new Rental(newMovie,5);

       Rental regRental=new Rental(regularMovie,5);

       Customer tom=new Customer("Tom");

       protected void setUp() throws Exception {

              super.setUp();

              tom.addRental(childRental);

              tom.addRental(newRental);

              tom.addRental(regRental);

       }

       public void testCaustomerName(){

       assertEquals("Tom",tom.getName());

       }

       public void testIteratorSize(){

       assertEquals(3,tom.getRentals().size());      

       }

       public void testIteratorName(){

              Enumeration rentals=tom.getRentals().elements();

              while (rentals.hasMoreElements()) {

                     Rental each = (Rental) rentals.nextElement();

                     switch(each.getMovie().getPriceCode()){

                     case Movie.CHILDRENS:

                            System.out.println("childrens");

                            assertEquals("HARRY POTTY",each.getMovie().getTitle());

                            assertEquals(3,each.getDayRented());

                            break;

                     case Movie.NEW_RELEASE:

                            System.out.println("new");

                            assertEquals("Ice Age 2",each.getMovie().getTitle());

                            assertEquals(5,each.getDayRented());

                            break;

                     case Movie.REGULAR:

                            System.out.println("regular");

                            assertEquals("Titanic",each.getMovie().getTitle());

                            assertEquals(5,each.getDayRented());

                            break;

                     }

              }

       }

       public void testOutput(){

              System.out.println(tom.statement());

       }

}