Parameter count mismatch on stub with lambda expression using Moq - unit-testing

Question

I get a 'parameter count mismatch' TargetParameterCountException when I want to test my Tenant repository:
The interface:
public interface ITenantRepository
{
IQueryable<Tenant> Get(Expression<Func<Tenant, bool>> filter = null,
Func<IQueryable<Tenant>, IOrderedQueryable<Tenant>> orderBy = null,
string includeProperties = null);
}
The test code:
var TenantRepository = new Mock<ITenantRepository>();
TenantRepository
.Setup(p => p.Get(It.IsAny<Expression<Func<Tenant, bool>>>(),
It.IsAny<Func<IQueryable<Tenant>,IOrderedQueryable<Tenant>>>() ,
It.IsAny<string>()))
.Returns(new Func<Expression<Func<Tenant, bool>>,
IQueryable<Tenant>>(expr => Tenants.Where(expr.Compile()).AsQueryable()));
Tenant TestTenant = TenantRepository.Object.Get(
t => t.TenantID == Tenant2.TenantID,
null,
null).FirstOrDefault();
The error occurs on the last line.

Answer 1

Found the solution for the correct parameters:
TenantRepository.Setup(p => p.Get(It.IsAny<Expression<Func<Tenant, bool>>>(),
It.IsAny<Func<IQueryable<Tenant>, IOrderedQueryable<Tenant>>>(),
It.IsAny<string>()))
.Returns(
(Expression<Func<Tenant, bool>> expr,
Func<IQueryable<Tenant>, IOrderedQueryable<Tenant>> orderBy,
string includeProperties) => Tenants.Where(expr.Compile()).AsQueryable());

Answer 2

I believe the problem resides in the return type of your mocked object: according to your interface, the method Get should return an IQueryable, but you are mocking it to return a Func<Expression<Func<Tenant, bool>>, IQueryable<Tenant>> instead.
Just keep in mind that returning a function is different from returning its result; in this case, you should create an expected IQueryable object and just tell Moq to return it. It doesn't make much sense to mock something using its expected behaviour - which looks like what you are trying to do here.