jUnit and DateFormat (EclEmma code coverage)

Question

I'm new to jUnit and I'm trying to deep more my knowledge about it. I searched on the web but didn't found anything to solve a couple of doubts.

This is the code:

public class StringConverter {

    public static String formatDate(Date date) {
        DateFormat sdf = new SimpleDateFormat("dd/MM/yyyy HH:mm:ss");
        return sdf.format(date);
    }

}

This is the jUnit4 Test Case:

public class StringConverterTest {

    @Test
    public void testFormatDate() {
        Calendar calendar = new GregorianCalendar(2013, 02, 13, 8, 30, 00);
        assertEquals("13/03/2013 08:30:00", StringConverter.formatDate(calendar.getTime()));
    }

}

The TestCase runs correctly without any problems but i have 2 simple questions/problems:

1) It's correct to test only the correct functionality of the method or should i test also null values and/or any particular exception?

2) When i run the code coverage with EclEmma it gives me 75% code coverage because the test case is not testing the constructor of the StringConverter class. Testing the StringConverter class constructor is not in my plan since the StringConverter class is a util class, so it won't be instanced. There is a way to exclude this from the code coverage?

Any advice wil be appreciated. Thanks.

Answer 1

1. To make sure that your method is bullet-proof, you should test every possible way to call it that you can think of, including with a null argument, unless you place a dire warning on the code that says:

   DO NOT EVER CALL THIS CODE WITH A null ARGUMENT.

2. If it is a utility class with only static methods, the no-argument constructor should be private and the class should be final, to emphasize this fact. Then maybe emma will leave you alone, especially if this constructor is empty.