### Question:
EventGroup { public Set<Event> getEvents() { Set<Event> clone = new LinkedHashSet<Event>(this.events.size(), 1f); clone.addAll(this.events); return Collections.unmodifiableSet(clone); } EventGroup();  EventGroup(List<Event> events);  EventGroup(Set<Event> events);  EventGroup(Event... events); Set<Event> getEvents(); void addEvents(Event... events); void clearEvents(); Event getMainEvent(); @Override String toString();  }### Answer:
@Test public void testConstructors() { assertNotNull(this.g.getEvents()); assertEquals(0, this.g.getEvents().size()); this.g = new EventGroup(this.event1); assertEquals(1, this.g.getEvents().size()); assertTrue(this.g.getEvents().contains(this.event1)); List<Event> l = new ArrayList<Event>(); l.add(this.event1); this.g = new EventGroup(l); assertEquals(1, this.g.getEvents().size()); assertTrue(this.g.getEvents().contains(this.event1)); Set<Event> s = new HashSet<Event>(); s.add(this.event1); this.g = new EventGroup(s); assertEquals(1, this.g.getEvents().size()); assertTrue(this.g.getEvents().contains(this.event1)); s.remove(this.event1); assertEquals(1, this.g.getEvents().size()); assertTrue(this.g.getEvents().contains(this.event1)); s.add(this.event2); s.add(this.event3); assertEquals(1, this.g.getEvents().size()); this.g = new EventGroup(s); assertEquals(2, this.g.getEvents().size()); }
@Test public void testConstructorsWithNull() { this.g = new EventGroup((List<Event>) null); assertNotNull(this.g.getEvents()); assertTrue(this.g.getEvents().isEmpty()); this.g = new EventGroup((Set<Event>) null); assertNotNull(this.g.getEvents()); assertTrue(this.g.getEvents().isEmpty()); this.g = new EventGroup((Event[]) null); assertNotNull(this.g.getEvents()); assertTrue(this.g.getEvents().isEmpty()); }
@Test public void testConstructorsWithNullElements() { List<Event> eventsList = new ArrayList<Event>(); eventsList.add(this.event1); eventsList.add(null); eventsList.add(this.event2); eventsList.add(this.event3); this.g = new EventGroup(eventsList); assertEquals(3, this.g.getEvents().size()); Set<Event> eventsSet = new HashSet<Event>(); eventsSet.add(this.event1); eventsSet.add(null); eventsSet.add(this.event2); eventsSet.add(this.event3); this.g = new EventGroup(eventsSet); assertEquals(3, this.g.getEvents().size()); this.g = new EventGroup(this.event1, null, this.event2, null, this.event3); assertEquals(3, this.g.getEvents().size()); }