Create a SqlException for testing

SqlExceptionMocker.cs

// .csproj
//    <PackageReference Include="System.Data.SqlClient" Version="4.3.0" />
//    <PackageReference Include="System.Reflection.TypeExtensions" Version="4.3.0" />

namespace HorribleThingsInHere
{
    using System.Data.SqlClient;
    using System.Linq;
    using System.Reflection;

    /// <summary>
    /// Workaround completely test-unfriendly sql error classes.
    /// Copy-paste from http://stackoverflow.com/a/1387030/10245
    /// Adjusted with updates in comments
    /// Adjusted to not use ctor indexes
    /// </summary>
    class SqlExceptionMocker
    {
        private static T Construct<T>(params object[] p)
        {
                var ctor = (
                    from ctors
                    in typeof(T).GetConstructors(
                        BindingFlags.NonPublic | BindingFlags.Instance)
                    where ctors.GetParameters().Count() == p.Count()
                    select ctors).Single();
                return (T)ctor.Invoke(p);
        }

        public static SqlException MakeSqlException(int errorNumber)
        {
            var collection = Construct<SqlErrorCollection>();
            var error =
                Construct<SqlError>(
                    errorNumber,
                    (byte) 2,
                    (byte) 3,
                    "server name",
                    "This is a mock SqlException",
                    "proc",
                    100,
                    null);

            typeof (SqlErrorCollection)
                .GetMethod("Add", BindingFlags.NonPublic | BindingFlags.Instance)
                .Invoke(collection, new object[] {error});

            var e =
                typeof (SqlException)
                    .GetMethod(
                        "CreateException",
                        new[] { typeof (SqlErrorCollection), typeof (string) })
                    .Invoke(null, new object[] {collection, "7.0.0"}) as SqlException;

            return e;
        }
    }
}