public void get_overdue_books_returns_all_books_which_are_overdue()
{
//given
var overDueBooksId = TestData.IssuedBooks.Where(i => DateTime.Now.Subtract(i.ReturnDate).Days > 0).Select(s => s.BookId).ToList();
var overDueBooks = TestData.Books.Where(b => overDueBooksId.Contains(b.BookId));
moqBookService.Setup(m => m.GetOverdueBooks()).Returns(overDueBooks);
var sut = new BookStoreService(moqStudentService.Object, moqBookService.Object, moqBookAllocationService.Object);
//when
var result = sut.GetOverdueBooks();
//then
Assert.IsInstanceOfType(result, typeof(IEnumerable <Book>));
moqBookService.Verify(v => v.GetOverdueBooks(), Times.Once);
}