CREATE DATABASE Test;
GO
USE Test
GO
CREATE TABLE dbo.Test
(
	TestId int NOT NULL
	,TestStr varchar(20) NOT NULL
);
INSERT INTO dbo.Test
VALUES (1, 'Test1')
	,(2, 'Test2')
	,(3, 'Test3');
GO
CREATE LOGIN TestRO WITH PASSWORD = 'TestRO', CHECK_POLICY = OFF;
CREATE USER TestRO FOR LOGIN TestRO WITH DEFAULT_SCHEMA=dbo;
ALTER ROLE db_datareader ADD MEMBER TestRO;

CREATE LOGIN TestRW WITH PASSWORD = 'TestRW', CHECK_POLICY = OFF;
CREATE USER TestRW FOR LOGIN TestRW WITH DEFAULT_SCHEMA=dbo;
ALTER ROLE db_datareader ADD MEMBER TestRW;
ALTER ROLE db_datawriter ADD MEMBER TestRW;
GO
SET ANSI_NULLS, QUOTED_IDENTIFIER ON;
GO
CREATE PROCEDURE dbo.ExecSQLRO
	@SQLString nvarchar(4000)
WITH EXECUTE AS 'TestRO'
AS
EXEC (@SQLString);
GO
CREATE PROCEDURE dbo.ExecSQLRW
	@SQLString nvarchar(4000)
WITH EXECUTE AS 'TestRW'
AS
EXEC (@SQLString);
GO
EXEC dbo.ExecSQLRO 'SELECT * FROM dbo.Test';
GO
EXEC dbo.ExecSQLRO 'DELETE dbo.Test WHERE TestId = 2';
GO
EXEC dbo.ExecSQLRW 'DELETE dbo.Test WHERE TestId = 2';

--USE master
--GO
--DROP DATABASE Test;
--DROP LOGIN TestRO;
--DROP LOGIN TestRW;