ElasticSearch 2.0 Nest Unit Testing with MOQ

The signature of the Func<T1, T2> passed to It.IsAny<T>() is not correct so the setup expectation will never be matched. The signature should be

It.IsAny<Func<SearchDescriptor<Person>, ISearchRequest>>()

A full working example

void Main(){    var people = new List<Person>    {        new Person { Id = 1 },        new Person { Id = 2 },    };    var mockSearchResponse = new Mock<ISearchResponse<Person>>();    mockSearchResponse.Setup(x => x.Documents).Returns(people);    var mockElasticClient = new Mock<IElasticClient>();    mockElasticClient.Setup(x => x        .Search(It.IsAny<Func<SearchDescriptor<Person>, ISearchRequest>>()))        .Returns(mockSearchResponse.Object);    var result = mockElasticClient.Object.Search<Person>(s => s);    Assert.AreEqual(2, result.Documents.Count()).Dump();}public class Person{    public int Id { get; set;}}

If you don't need to stub the client then you can simply use a real client and set the IConnection to an instance of InMemoryConnection

var pool = new SingleNodeConnectionPool(new Uri("http://localhost:9200"));// pass an instance of InMemoryConnection so that requests are not // **actually** sentvar connectionSettings = new ConnectionSettings(pool, new InMemoryConnection())        .PrettyJson()        .DisableDirectStreaming()        .OnRequestCompleted(response =>            {                // log out the request                if (response.RequestBodyInBytes != null)                {                    Console.WriteLine(                        $"{response.HttpMethod} {response.Uri} \n" +                        $"{Encoding.UTF8.GetString(response.RequestBodyInBytes)}");                }                else                {                    Console.WriteLine($"{response.HttpMethod} {response.Uri}");                }                // log out the response                if (response.ResponseBodyInBytes != null)                {                    Console.WriteLine($"Status: {response.HttpStatusCode}\n" +                             $"{Encoding.UTF8.GetString(response.ResponseBodyInBytes)}\n" +                             $"{new string('-', 30)}\n");                }                else                {                    Console.WriteLine($"Status: {response.HttpStatusCode}\n" +                             $"{new string('-', 30)}\n");                }            });var client = new ElasticClient(connectionSettings);

This way you could also capture the requests if you needed to. You could take this a step further and create your own IConnection implementation that returns stub responses.