I would be keen to have the ability to run multiple validation sub-steps for a test step. For example, I have an MSMQ read step. Against this message data I would like to run: the Xml Schema validation test step to ensure the whole message is valid against schema; and a also run a custom validation step that test certain parts of the message against business rules.

    public override Stream Execute(Stream data, Context context)
    {
        < validation logic here>            
        data.Position = 0; // reset position so stream is available to subsequent sub-steps.
        return data;
    }