Question

Please, I am new to Java. How can I write a JUnit test for the program below:

Program to Test:

package codekeeper;

/**
 *
 * @author henryjoseph
 */
import java.util.*;
import java.io.*;

public class CodeKeeper {

    ArrayList<String> list;  //no specific amount..

    String[] codes = {"alpha","lambda","gamma","delta","zeta"};

    public CodeKeeper (String[] userCodes)
    {
        list = new ArrayList<String>();

        for(int i =0; i<codes.length;i++)
           addCode(codes[i]);

        for(int i =0; i<userCodes.length;i++)
            addCode(userCodes[i]);

        for(String code:list)
            System.out.println(code);
    }

    final void addCode(String code)
    {
        if(!list.contains(code))
            list.add(code);
    }

    public static void main(String[] args) {
        System.out.print("Enter your name and press Enter: ");
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        String name = null;
        String[] argu = new String[] {name};
        try {
            name = br.readLine();

            argu = new String[] {name} ;
        }catch (IOException e) {
            System.out.println("Error!");
            System.exit(1);
        }
        CodeKeeper keeper = new CodeKeeper(argu);
    }
}

Sample Test Code:

public class MyClassTest {
    @Test
    public void testMultiply() {
        MyClass tester = new MyClass();
        assertEquals("Result", 50, tester.multiply(10, 5));
    }
}

Is this a standard way of writing the Junit Tests?

Answer 1

Some background first then some examples. When you write unit tests against your code you are testing a very specific and finite case of your application. What that means is that each unit test should cover at most one (1) scenario that a function (method) can receive. If you want to test multiple functions together you would be performing integration testing. Now if we take the following function that you have declared:

    final void addCode(String code)          
{   
           if(!list.contains(code))           
               list.add(code);           
} 

Assume that codeKeeper is properly initialized.
An appropriate unit test would look like this:

@Test(expected= NullPointerException.class)   
public void testAddCode_1() throws Exception  
{  
    codeKeeper.addCode(null);  
}  

Another appropriate usage is the following:

@Test()  
public void testAddCode_2() throws Exception  
{  
       codeKeeper.addCode("myMagicCode");
       assertTrue(codeKeeper.getList().contains("myMagicCode");  
}