error TestQueryable when mock nhibernate query with multiple fetches

[ivan-luxoft]

I have a problem with mocking query by TestQueryable
the next request is failed:

repository.Create().GetQueryable()
                                  .FetchMany(x => x.InternalCollection)
                                  .ThenFetchMany(x => x.InternalInternalCollection)
                                  .Single(x => x.Id == id)

the TestQueryable fails in method AvoidFetch because the one of the fetches doenst have node.Arguments[0] as MethodCallExpression, it has a constant

I fix it locally as

private static Expression AvoidFetch(MethodCallExpression node) =>
  !ExpressionTreeModifier.IsFetchMethod(node.Method)
                    ? (Expression)node
                    : node.Arguments[0] is MethodCallExpression methodNode
                        ? ExpressionTreeModifier.AvoidFetch(methodNode)
                        : node.Arguments[0];

I'm not sure that it is the right way, but it works for me, and all my tests/queryable mocks