µJava Is not killing Mutants?

Question

i am using µJava for mutation testing of my java program. as i am learning mutation testing.

i have 2 classes

1 : Parent

public class Parent 
{
public String temp;
public int number;

public Parent(String temp)
{
    this.temp = temp;
    this.number = 20;
}

public String printTemp()
{       
    return "temp is : "+temp+number;
} 
}

and 2 : Child

public class Child extends Parent
{
public int number;

public Child(String temp)
{
    super(temp);
    this.number = 5;
}

public String printTemp()
{
    String temp = "i am fake !";
    int number = 766;
    return "temp is : "+super.temp+this.number+"c";
}
}

and i am applying IOD operation of muJava. `hence it is generating mutant . it is deleting overridden method printTemp of child class.

my TestCase is :

public class MyTest
 {
    public String test1 ()
      {  
      String result;

     Parent p1 = new Parent("i am temp of parent");

      Child c1 = new Child("i am temp of child");

      Parent p2 = new Child("i am both !");

      result = ""+ c1.printTemp() + p1.printTemp() + p2.printTemp(); 

      return result;
      }
   }

But when i am running Mutation Testing , i have found the mutant lived. i want to kill it ! What can i do ??

No idea what µJava is and I do not see anything in the code you provided that is not vanilla Java. As a side note: `c1` is also of type `Parent` as `Child` is a subclass of `Parent` — hotzst, Oct 03 '15 at 20:02

score 1 · Answer 1 · answered Oct 05 '15 at 18:15

MuJava has switched its testing infrastructure to JUnit (see https://cs.gmu.edu/~offutt/mujava/, Section III.3). This means that you should write a JUnit test, which not only covers the code but also asserts on the result.

Example:

@Test
public void testPrintTempChild() {
    Child c = new Child("Child");
    String actual = c.printTemp();
    String expected = "temp is : Child5c"; 
    assertEquals(expected, actual);
}

@Test
public void testPrintTempParent() {
    Parent p = new Parent("Parent");
    String actual = p.printTemp();
    String expected = "temp is : Parent20";
    assertEquals(expected, actual);
}

If you apply the IOD mutation operator, the first test should detect that mutant (i.e., it should fail because printTemp returns "temp is : Child20").

As an additional comment, the reference p2 in your test code is also an instance of Child, so c1.printTemp() and p2.printTemp() both invoke the method printTemp in your class Child.

Can you justify that why i need to put assert ? and what it actually does ? — KrunalParmar, Oct 05 '15 at 18:29
A call to assertEquals raises an AssertionError (which will make the test fail) if the expected value and the actual value differ. You might want to take a look at [wiki](https://github.com/junit-team/junit/wiki/Assertions) and [javadoc](http://junit.org/apidocs/org/junit/Assert.html) for more details on JUnit's assert methods. Keep in mind that the overall goal is to make a test fail on a mutant. So, unless your test includes an assertion that checks the actual outcome of the tested method, it can only detect a mutant if that mutant raises an unexpected exception. — Rene Just, Oct 07 '15 at 17:05

µJava Is not killing Mutants?

1 Answers1