assertEquals uses the equals() method: 
    public void testAEqualsA() {
        Fraction a = Fraction.getFraction(17, 56);
        assertEquals(a, a);
    }
     
    public void testAEqualsA() {
        Fraction a = Fraction.getFraction(17, 56);
        assertEquals(a, a);
    }
     
    public void testAEqualsA2() {
        Fraction a = Fraction.getFraction(17, 56);
        Fraction b = Fraction.getFraction(17, 56);
        assertEquals(a, b);
    }