public async void Test4GetAsync()
{
var mockClient = new Mock <IMongoClient>();
var mockContext = new Mock <IMongoContext>();
var client = mockClient.Object;
var mockCollection = CreateMockCollection();
var collection = mockCollection.Object;
var session = new Mock <IClientSessionHandle>().Object;
var options = new ChangeStreamOptions();
var cancellationToken = new CancellationTokenSource().Token;
Book document = new Book();
document.Author = "asdas";
document.BookName = "sadasd";
document.Id = ObjectId.GenerateNewId().ToString();
collection.InsertOne(document);
var bookMock = new Mock <IFindFluent <Book, Book> >();
mockContext.Setup(x => x.GetCollection <Book>("Book")).Returns(mockCollection.Object);
BookstoreDatabaseSettings setting = new BookstoreDatabaseSettings();
setting.BooksCollectionName = "Book";
var mockIDBsettings = new Mock <IOptions <BookstoreDatabaseSettings> >();
mockIDBsettings.Setup(x => x.Value).Returns(setting);
//mockCollection.Setup(x => x.FindAsync(It.IsAny<ExpressionFilterDefinition<Book>>(), null, cancellationToken))
// .Returns(bookMock.Object);
BookService service = new BookService(mockIDBsettings.Object, mockContext.Object);
//service.Create(document);
var result = await service.GetBooksAsync();
mockContext.Verify(x => x.GetCollection <Book>("Book"), Times.Once);
var options1 = new FindOptions <Book>(); // no projection
// var filterExpression = (Expression<Func<Book, bool>>)(x => x.BookName == "sadasd");
var filter = It.IsAny <ExpressionFilterDefinition <Book> >();
var filter1 = It.IsAny <FilterDefinition <Book> >();
//var filter2 = It.IsAny<EmptyFilterDefinition<Book>>();
//FindFluent<Book, Book> fluent;
//
//mockCollection.Verify(x=>x.Find(filterExpression, null), Times.Once);
//
//var filterDefinition = Builders<Book>.Filter.Eq("BookName", "sadasd");
var filterExpression = (Expression <Func <Book, bool> >)(x => x.BookName == "sadasd");
IMongoCollectionExtensions.FindAsync(collection, session, filterExpression, options1, cancellationToken);
mockCollection.Verify(m => m.FindAsync <Book>(session, It.IsAny <ExpressionFilterDefinition <Book> >(), options1, cancellationToken), Times.Once);
mockCollection.Verify(m => m.FindAsync <Book>(FilterDefinition <Book> .Empty, null, CancellationToken.None), Times.Once);
//
//
//
//
//
}