1. A method of generating scenario data within a programmable processing system, the method comprising: receiving directives comprising: configuration directives comprising a number of fields in a record, a number of threads to be initiated for generating the scenario data and a location to send the scenario data; constants directives, wherein constants directives comprise constant data to be inserted in each record in a datastream, the constant data based on a key value of an indicated field; change directives, wherein change directives list fields that change within a set of a specified number of related records; value directives, wherein value directives provide valid values for at least one field in the record; probabilities directives, wherein a set of probabilities directives comprise at least one percentage, the percentage specifying a proportion of the set of related records wherein a field in the set of related records comprises a particular value; and generating a datastream of records in accordance with the received directives.