How to throw a SqlException when needed for mocking and unit testing?

Question

I am trying to test some exceptions in my project and one of the Exceptions I catch is SQlException.

It seems that you can't go new SqlException() so I am not sure how I can throw an exception especially without somehow calling the database (and since these are unit tests it is usually advised not to call the database since it is slow).

I am using NUnit and Moq, but I am not sure how to fake this.

Responding to some of the answers that seem to all be based on ADO.NET, note that I am using Linq to Sql. So that stuff is like behind the scenes.

More info as requested by @MattHamilton:

System.ArgumentException : Type to mock must be an interface or an abstract or non-sealed class.          at Moq.Mock`1.CheckParameters()   at Moq.Mock`1..ctor(MockBehavior behavior, Object[] args)   at Moq.Mock`1..ctor(MockBehavior behavior)   at Moq.Mock`1..ctor() 

Posts to the first line when it tries to mockup

 var ex = new Mock<System.Data.SqlClient.SqlException>();  ex.SetupGet(e => e.Message).Returns("Exception message"); 

Answer 1

You can do this with reflection, you will have to maintain it when Microsoft make changes, but it does work I just tested it:

public class SqlExceptionCreator {     private static T Construct<T>(params object[] p)     {         var ctors = typeof(T).GetConstructors(BindingFlags.NonPublic | BindingFlags.Instance);         return (T)ctors.First(ctor => ctor.GetParameters().Length == p.Length).Invoke(p);     }      internal static SqlException NewSqlException(int number = 1)     {         SqlErrorCollection collection = Construct<SqlErrorCollection>();         SqlError error = Construct<SqlError>(number, (byte)2, (byte)3, "server name", "error message", "proc", 100);          typeof(SqlErrorCollection)             .GetMethod("Add", BindingFlags.NonPublic | BindingFlags.Instance)             .Invoke(collection, new object[] { error });           return typeof(SqlException)             .GetMethod("CreateException", BindingFlags.NonPublic | BindingFlags.Static,                 null,                 CallingConventions.ExplicitThis,                 new[] { typeof(SqlErrorCollection), typeof(string) },                 new ParameterModifier[] { })             .Invoke(null, new object[] { collection, "7.0.0" }) as SqlException;     } }       

This also allows you to control the Number of the SqlException, which can be important.