@Test
 public void testAddAttendeeFalse() throws Exception {
   assertFalse(e2.addAttendee(a1));
   assertTrue(e2.isAttendedBy(a1));
 }
 @Test
 public void testAddAttendeeNonEmpty() throws Exception {
   assertTrue(e2.addAttendee(a2));
   assertTrue(e2.isAttendedBy(a2));
 }
 @Test
 public void testIsAttendedByTrue() throws Exception {
   assertTrue(e2.isAttendedBy(a1));
 }
 @Test
 public void testAddAttendeeEmpty() throws Exception {
   assertTrue(e1.addAttendee(a1));
   assertTrue(e1.isAttendedBy(a1));
 }
 @Test
 public void testIsAttendedByFalse() throws Exception {
   assertFalse(e1.isAttendedBy(a1));
 }