Testes usando JUnit

public static String format(Object value)
{
    	DecimalFormatSymbols decimalFormat = new DecimalFormatSymbols();
        decimalFormat.setDecimalSeparator(',');
        decimalFormat.setGroupingSeparator('.');

        DecimalFormat myFormatter = new DecimalFormat("##,###,###,##0.00", decimalFormat);
        
        return myFormatter.format(value);
}

public void testFormat() {
	DoubleHelper helper = new DoubleHelper(new Double(1000000.565656565)); 
	String result = helper.format();
	String expected = new String("1.000.000,57");
	assertEquals(expected, result);
}