Elasticsearch C# Nest unit tests with Moq : fail to mock concrete class

[Nicolas_Rey]

Hi,

I need to mock some methods and properties in Nest.IElasticClient interface that is used in my repo. As example I need to stub the Indices.Exists() method to return an ExistsResponse having an Exists property returning true.

The problem is that the concrete class has no interface implementation, nor setter on the Exists property, and is not declared virtual neither in Nest lib:

public class ExistsResponse : ResponseBase
{
    public ExistsResponse();
    public bool Exists { get; }
}

public ExistsResponse Exists(Indices index, Func<IndexExistsDescriptor, IIndexExistsRequest> selector = null);

So for the mocking I tried to set the property anyway on the concrete class, but it failed with all the following methods, I have no idea on how to do ...

/* Fail with exception :
System.NotSupportedException : Unsupported expression: x => x.Exists
    Non-overridable members (here: ExistsResponse.get_Exists) may not be used in setup / verification expressions.
*/
    var mock1 = new Mock<ExistsResponse>();
    obj.SetupGet(f => f.Exists).Returns(true);

/* Fail with exception :
 System.NotSupportedException : Unsupported expression: f => f.Exists
    Non-overridable members (here: ExistsResponse.get_Exists) may not be used in setup / verification expressions.
*/
    var mock2 = Mock.Of<ExistsResponse>(x => x.Exists == true);

/* Fail with exception :
System.ArgumentException : Property set method not found.
*/
    var mock3 = new ExistsResponse();
    var property = typeof(ExistsResponse).GetProperty("Exists", BindingFlags.Public | BindingFlags.Instance);
    property.SetValue(mock3, true);

/* Fail with exception :
System.NullReferenceException (setter is null)
*/
    var mock4 = new ExistsResponse();
    var setter = property.GetSetMethod(true);
    setter.Invoke(mock4, new object[] { true });


    // My Mock on the Indices.Exists method
    var elasticMock = new Mock<IElasticClient>();
    elasticMock
    .Setup(x => x.Indices.Exists(It.IsAny<string>(), null))
    .Returns(/*** my stubbed object here ***/); // <== how to stub it to return a ExistsResponse.Exists = false ?

My libs

Nest 7.12.1
Moq 4.15.2
XUnit 2.4.1
.Net 5

Thank you for your help