### Question:
Booking { public static List<String> extractBookingIds(List<Booking> bookings) { List<String> result = new ArrayList<>(); for (Booking booking : bookings) { result.add(booking.getBookingId()); } return result; } Booking(TargetingChannel targetingChannel, List<Range> ranges, double price, String advId, long requestCount);  Booking(String id, Map source); static Number extractNumber(Object obj); static Map<String, Booking> buildBookingMap(List<Booking> bookings); static List<String> extractBookingIds(List<Booking> bookings); String getId(); List<String> getDays(); String getBookingId(); String getAdvId(); Double getPrice(); Long getAmount(); TargetingChannel getQuery();  }### Answer:
@Test public void extractBookingIds() { TargetingChannel tc1 = new TargetingChannel(); List<Range> ranges = new ArrayList<>(); Range r1 = new Range("2018-01-05", "2018-01-05", "0", "23"); ranges.add(r1); Booking bk1 = new Booking(tc1, ranges, 0, "", 0); List<Booking> bks1 = new ArrayList<>(); bks1.add(bk1); assertEquals(1, Booking.extractBookingIds(bks1).size(), 0); }