Junit testing for a boolean method

问题:

I have problem writing a testcase to this method below: EvenNum(double)

public class OddEven {

/**
 * @param args
 */

public boolean evenNum(double num)
{
    if(num%2 == 0)
    {
        System.out.print(true);
        return true;
    }
    else
    {
        System.out.print(false);
        return false;
    }

}

This is the testcase I wrote but I think I have an inheritance problem or a logical problem in this test case. Should be a very simple one but can't figure out. Here is the code I wrote:

import static org.junit.Assert.*;
import org.junit.Test;

public class OddEvenTest {
    @Test
    public void testEvenNum() {
        boolean ans = true;
        boolean val;
        double num= 6;

        val = OddEven.EvenNum(num) // cant inherit the method dont know why???

        assertEquals(ans,val);
    }

}

回答1:

Two things :

• You are invoking a non-static method statically. The method should be declared static:

  public static boolean evenNum(double num) {

  }

• You didn't type the name of the method correctly. Look closely. Also consider renaming it something more readable like, isEven(...)

回答2:

You have a number of issues:

• you are attempting to call a non-static method statically
• method names in java are case sensitive and you've mixed up the case.

I corrected some things for you and just verified the code below:

OddEven.java:

public class OddEven {

        public boolean evenNum(double num)
        {
            if(num%2 == 0)
            {
                System.out.print(true);
                return true;
            }
            else
            {
                System.out.print(false);
                return false;
            }

        }
}

OddEvenTest.java

import static org.junit.Assert.*;
import org.junit.Test;

public class OddEvenTest {

    @Test
    public void testEvenNum() {
        boolean ans = true;
        boolean val;
        double num = 6;
        OddEven oddEven = new OddEven();

        val = oddEven.evenNum(num);
        assertEquals(ans,val);
    }

}

Assuming the calls to System.out.println() in OddEven are strictly for debugging, the whole thing could be collapsed down to:

OddEven.java

public class OddEven {
    public boolean evenNum(double num) {
        return num%2 == 0;
    }
}

OddEvenTest.java

import static org.junit.Assert.*;
import org.junit.Test;

public class OddEvenTest {

    @Test
    public void testEvenNum() {
        OddEven oddEven = new OddEven();
        assertTrue(oddEven.evenNum(6));
        assertFalse(oddEven.evenNum(5));
    }
}

The code is now shorter and the unit test even covers an odd case for good measure.

回答3:

This seems like testing gone mad to me, and programming gone mad too. All the method does is evaluate num % 2 == 0. You may as well just code that everywhere required and throw away both the method and its tests. If you must keep the method, it relies on a mathematical identity, you don't need to test those. You may as well test 1+1==2.