import junit.framework.*;
 
 /**
    A class to test the Day class with JUnit.
 */
 public class DayTest extends TestCase
 {
    /**
       This test tests the addDays method with positive 
       parameters.
    */
    public void testAdd()
    {
       for (int i = 1; i <= MAX_DAYS; i = i * INCREMENT)
       {
          Day d1 = new Day(1970, 1, 1);
          Day d2 = d1.addDays(i);
          assert d2.daysFrom(d1) == i;      
       }
    }
 
    /**
       This test tests the addDays method with negative 
       parameters.
    */
    public void testAddNegative()
    {
       for (int i = 1; i <= MAX_DAYS; i = i * INCREMENT)
       {
          Day d1 = new Day(1970, 1, 1);
          Day d2 = d1.addDays(-i);
          assert d1.daysFrom(d2) == i;      
       }
    }
 
    /**
       This test tests the daysFrom method.
    */
    public void testDaysFrom()
    {
       Day d1 = new Day(1970, 1, 1);
       Day d2 = new Day(2001, 1, 1);
       int n = d1.daysFrom(d2);
       Day d3 = d2.addDays(n);
       assert d1.getYear() == d3.getYear();      
       assert d1.getMonth() == d3.getMonth();      
       assert d1.getDate() == d3.getDate();      
    }
 
    /**
       This test tests arithmetic around the Gregorian
       calendar change.
    */
    public void testGregorianBoundary()
    {
       Day d1 = new Day(1580, 1, 1);
       Day d2 = d1.addDays(MAX_DAYS);
       Day d3 = d2.addDays(-MAX_DAYS);
       assert d3.daysFrom(d1) == 0;      
    }
 
    private static final int MAX_DAYS = 10000;
    private static final int INCREMENT = 10;
}