public void ClearEmptyDiscardList()
{
var bookManagerMock = new Mock <IBookManager>();
bookManagerMock.Setup(m =>
m.GetAllBooksInDiscardList())
.Returns(new List <Book>());
var bookAPI = new BookAPI(null, bookManagerMock.Object);
var result = bookAPI.ClearDiscardList();
Assert.AreEqual(ClearDiscardListStatusCodes.NoDiscardBooksToClear, result);
bookManagerMock.Verify(
m => m.ClearDiscardList(It.IsAny <List <Book> >()), Times.Never);
}