def test_book_can_un_reserve_book():
book = Book('TITLE', 'DESCRIPTION', 'ISBN')
book.reserve('RESERVER')
book.reserve('ANOTHER RESERVER')
book.reserve('YET ANOTHER RESERVER')
book.un_reserve('ANOTHER RESERVER')
book.un_reserve('RESERVER')
book.un_reserve('YET ANOTHER RESERVER')
assert_equals(0, len(book.reservations))
def test_book_cannot_un_reserve_book_when_not_reserved_by_you():
book = Book('TITLE', 'DESCRIPTION', 'ISBN')
book.reserve('RESERVER')
book.un_reserve('ANOTHER RESERVER')
