关于junit测试用例

Question

I am new to the world of Junit test cases , I just wanted to know let say if I developed a program

class MapDemo1
{static final Logger logger = Logger.getLogger(MapDemo1.class);
     /**
     *  
     */
    public static void main(String arg[])
     {PropertyConfigurator.configure("src/log4j.properties");
     logger.info("-->Map");
    // Map map=new TreeMap();

         Map map=new HashMap();//HashMap key random order.
      //   System.out.println("Amit".hashCode());
         map.put("Amit","Java");
         map.put("Amit","Javas");
        // map.put("mAit","J2EE");
         //map.put("Saral","J2rrrEE");
         /*map.put("ty","Spring");
         map.put("Anupam","Hibernate");
         map.put("Ravi",".Net");
         map.put("Saral","Andriod");//same key but different value 
         map.put("Nitin","PHP");
         map.put("hj","Spring1");*/
         System.out.println("There are "+map.size()+" elements in the map.");
         System.out.println("Content of Map are...");
         Set s=map.entrySet();
         Iterator itr=s.iterator();
         while(itr.hasNext())
         {
             Map.Entry m=(Map.Entry)itr.next();
             System.out.println(m.getKey()+"\t"+m.getValue()+"\t"+ m.hashCode());
          }
]
}

Now please advise what are the junit test cases for this and how they will be written in seprate class.

Answer 1

As is, this program is not testable using JUnit -- it's too small, and it's all in one method. To make it testable, you need to break it apart into parts that do just one thing.

One such part could be populateMap() , a method that created the HashMap and added the values. Then you could add one or two tests that called that method and tested the size and content of the map.

Printed output is also hard (if not impossible) to test. One way to deal with this would be to put the code that printed output into a method that accepted a PrintWriter as a parameter. In the real program, call it and pass it something connected to System.out . In a test, you could call it with a PrintWriter connected to a StringWriter , and then examine the contents of that StringWriter .

In general, you don't test programs with JUnit; you test units . A unit is either a class, or a small group of tightly-coupled classes, that provide some kind of well-defined service to the rest of a program. For example, a class like StringBuilder is a fairly large and complex unit, and hopefully you can imagine dozens or hundreds of tests you might write for it.