Test leap years

src/main/java/com/kosherjava/zmanim/hebrewcalendar/JewishDate.java

@@ -309,7 +309,8 @@ public int getMoladChalakim() {
      *            the month. As with other cases in this class, this is 1-based, not zero-based.
      * @return the number of days in the month in the given year
      */
-    private static int getLastDayOfGregorianMonth(int year, int month) {
+    // @VisibleForTesting
+	protected static int getLastDayOfGregorianMonth(int year, int month) {
         return YearMonth.of(year, month).lengthOfMonth();
     }
 
@@ -1280,12 +1281,8 @@ public Object clone() {
         return clone;
     }
 
-    /**
-     * Overrides {@link Object#hashCode()}.
-     * @see Object#hashCode()
-     */
-    @Override
-    public int hashCode() {
-        return Integer.hashCode(gregorianAbsDate);
-    }
+	@Override
+	public int hashCode() {
+		return gregorianAbsDate;
+	}
 }

src/test/java/com/kosherjava/zmanim/hebrewcalendar/UT_DaysInJewishMonth.java

@@ -4,8 +4,14 @@
 
 package com.kosherjava.zmanim.hebrewcalendar;
 
+import static org.junit.Assert.assertEquals;
+
 import org.junit.*;
 
+import java.time.DayOfWeek;
+import java.time.LocalDate;
+import java.time.Month;
+
 /**
  * Validate the days in a Hebrew month (in various types of years) are correct.
  */
@@ -111,4 +117,15 @@ private void assertShalemLeap(int year) {
 		Assert.assertTrue(jewishDate.isJewishLeapYear(  ));
 	}
 
+	@Test
+	public void earlyGregorian() {
+		LocalDate localDate = LocalDate.of(1582, Month.OCTOBER, 15);
+		JewishDate jewishDate = new JewishDate(localDate);
+
+		assertEquals(DayOfWeek.FRIDAY, localDate.getDayOfWeek());
+		assertEquals(5343, jewishDate.getJewishYear());
+		assertEquals(JewishDate.TISHREI, jewishDate.getJewishMonth());
+		assertEquals(19, jewishDate.getJewishDayOfMonth());
+	}
+
 } // End of UT_DaysInJewishMonth class

src/test/java/com/kosherjava/zmanim/hebrewcalendar/UT_JewishLeapYear.java

@@ -4,8 +4,12 @@
 
 package com.kosherjava.zmanim.hebrewcalendar;
 
+import static org.junit.Assert.assertEquals;
+
 import org.junit.*;
 
+import java.time.Month;
+
 /**
  * Verify correct calculations of when a Hebrew leap year occurs.
  */
@@ -63,4 +67,39 @@ private void shouldNotBeLeapYear(int year) {
 		Assert.assertFalse(jewishDate.isJewishLeapYear(  ));
 	}
 
+	@Test
+	public void icu() {
+		for (int y = 0; y < 10000; y++) {
+			assertEquals(isLeapYearICU(y), JewishDate.isJewishLeapYear(y));
+		}
+	}
+
+	/** android.icu.util.HebrewCalendar */
+	public static boolean isLeapYearICU(int year) {
+		int x = (year * 12 + 17) % 19;
+		return x >= ((x < 0) ? -7 : 12);
+	}
+
+	@Test
+	public void leapYears(){
+		final int MONTH_FEBRUARY = Month.FEBRUARY.getValue();
+		for (int y = 0; y < 10000; y++) {
+			assertEquals(isLeapYearWiki(y), JewishDate.getLastDayOfGregorianMonth(y, MONTH_FEBRUARY) == 29);
+		}
+	}
+
+	/** https://en.wikipedia.org/wiki/Leap_year#Algorithm */
+	private static boolean isLeapYearWiki(int year) {
+		if (year % 4 != 0) {
+			return false;
+		}
+		if (year % 100 != 0) {
+			return true;
+		}
+		if (year % 400 != 0) {
+			return false;
+		}
+		return true;
+	}
+
 } // End of UT_JewishLeapYear class