Answer 2: Expanding the test suite

import junit.framework.TestCase;

public class FractionTest extends TestCase {

    public void testAddition() {
      
        Fraction half = new Fraction(2, 4);
        Fraction fourth = new Fraction(1, 4);
        
        Fraction actual = half.add(fourth);
        Fraction expected = new Fraction(3, 4);
        assertEquals(expected, actual);
        
    }
    
    public void testSubtraction() {
      
        Fraction half = new Fraction(2, 4);
        Fraction fourth = new Fraction(1, 4);
        
        Fraction actual = half.subtract(fourth);
        Fraction expected = fourth;
        assertEquals(expected, actual);
        
    }
    
    public void testAddNumberToItself() {
      
        Fraction half = new Fraction(2, 4);
        Fraction actual = half.add(half);
        Fraction expected = new Fraction(1, 1);
        assertEquals(expected, actual);
        
    }
    
}

Notice the duplication of code. Duplication of code is bad!