use master;
create login TestLogin with password = '', check_policy = off;
exec sys.sp_addlinkedserver @server = N'loopback', @srvproduct = N'', @provider = N'SQLNCLI', @datasrc = @@servername;
exec sys.sp_serveroption @server = N'loopback', @optname = N'data access', @optvalue = N'true';
exec sys.sp_addlinkedsrvlogin @rmtsrvname = N'loopback', @useself = N'false', @locallogin = null, @rmtuser = N'TestLogin', @rmtpassword = N'';
go

create database Test001;
alter authorization on database::Test001 to sa;
go

use Test001;
go

create procedure dbo.spTest
as
begin
 select top (1) system_user, * from loopback.master.dbo.spt_values;
end;
go

exec dbo.spTest;
go

alter procedure dbo.spTest
with execute as 'dbo'
as
begin
 select top (1) system_user, * from loopback.master.dbo.spt_values;
end;
go

exec dbo.spTest;
go

alter database Test001 set trustworthy on;
go

exec dbo.spTest;
go

use master;
exec sys.sp_dropserver @server = N'loopback', @droplogins = N'droplogins';
drop login TestLogin;
go

drop database Test001;
go