add assertion

src/test/java/nl/tudelft/queue/service/TimeSlotServiceTest.java

@@ -21,6 +21,7 @@ import static org.assertj.core.api.Assertions.assertThat;
 import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.Mockito.when;
 
+import java.util.Comparator;
 import java.util.List;
 
 import javax.transaction.Transactional;
@@ -112,6 +113,9 @@ class TimeSlotServiceTest {
 				lastSlot.getSlot().getClosesAt().isBefore(oopNowSlottedLab1Slot.getOpensAt().plusHours(10L)))
 						.isTrue();
 
+		assertThat(newTimeSlots).hasSameSizeAs(listOfInitialSlots)
+				.isSortedAccordingTo(Comparator.comparing(TimeSlot::getOffsetSequenceNumber));
+
 	}
 
 	private SlottedLab fetchAndCast(long labID) {