1. A method for simulating a behavior of a spooler, comprising: receiving an output file produced by the spooler as a result of the execution of a unit of work in a data processing apparatus, said unit of work being submitted to the spooler by a data processing automation program, the data processing automation program executing using a memory on the data processing apparatus and performing normal operations, wherein executing the data processing automation program using the memory on the data processing apparatus and performing normal operations comprises an operation of the instance of the data processing automation program in a customer environment; extracting from the received output file at least one collection of data, wherein said at least one collection of data includes data necessary to the data processing automation program for performing a data processing automation function; switching the data processing automation program that is executing using the memory on the data processing apparatus from the operation in the production data processing environment to operate in a test environment while continuing to use the memory in the data processing apparatus, wherein the data processing automation program includes a selector module, the selector module enabling the data processing automation program to select between a data source to perform the normal operations in the customer environment and another data source to operate in the test environment; and causing the data processing automation program operating in the test environment to receive said at least one collection of data instead of retrieving the necessary data from the spooler.