public void get_books_returns_all_available_books()
{
//given
moqBookService.Setup(m => m.GetAllBooks()).Returns(TestData.Books);
var sut = new BookStoreService(moqStudentService.Object, moqBookService.Object, moqBookAllocationService.Object);
//when
var result = sut.GetAllBooks();
//then
Assert.IsInstanceOfType(result, typeof(IEnumerable <Book>));
Assert.AreEqual(TestData.Books.Count, result.Count());
moqBookService.Verify(v => v.GetAllBooks(), Times.Once);
}