Connection.Open() InvalidOperationException

The following test throws an expection. I am using Typemock 6.0.4.0

 [Test, Isolated]
        public void MyTest()
        {
            var fakeSqlConnection = Isolate.Fake.Instance<SqlConnection>();
            Isolate.Swap.AllInstances<SqlConnection>().With(fakeSqlConnection);
            Isolate.WhenCalled(() => fakeSqlConnection.Open()).IgnoreCall();

            SqlConnection sqlConnection = new SqlConnection();
            sqlConnection.Open();
        }

Exception
***************************************
System.Reflection.TargetInvocationException occurred
Message="Exception has been thrown by the target of an invocation."
Source="mscorlib"
StackTrace:
at System.RuntimeMethodHandle._InvokeMethodFast(Object target, Object[] arguments, SignatureStruct& sig, MethodAttributes methodAttributes, RuntimeTypeHandle typeOwner)
at System.RuntimeMethodHandle.InvokeMethodFast(Object target, Object[] arguments, Signature sig, MethodAttributes methodAttributes, RuntimeTypeHandle typeOwner)
at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture, Boolean skipVisibilityChecks)
at System.Delegate.DynamicInvokeImpl(Object[] args)
at System.Delegate.DynamicInvoke(Object[] args)
at f7.b(Boolean A_0)
at f7.g()
at NetQuote.Internet.Tests.Common.Facade.Calling_Application_CheckForDuplicateApplications.MyTest() in C:DataProjectsNetQuote runkNetQuote.Internet.TestsCommonFacadeCalling_Application_CheckForDuplicateApplications.cs:line 41
InnerException: System.InvalidOperationException
Message="The ConnectionString property has not been initialized."
Source="System.Data"
StackTrace:
at System.Data.SqlClient.SqlConnection.PermissionDemand()
at System.Data.SqlClient.SqlConnectionFactory.PermissionDemand(DbConnection outerConnection)
at System.Data.ProviderBase.DbConnectionClosed.OpenConnection(DbConnection outerConnection, DbConnectionFactory connectionFactory)
at System.Data.SqlClient.SqlConnection.Open()