At execution, the MCF simulator links the MHP to the online tester library rather than to the library provided by the MCF. At linkage to the online tester, the functions used by the MHP are replaced by functions for the online tester. These functions are called MCF simulation functions.

To use the MCF simulator, the user must first write a user service definition, defining the MHP for which functions are to be replaced as a simulate MHP. A simulate MHP is an MHP that uses MCF simulation functions and runs in test mode (that is, all the facilities of the online tester can be used). A simulate MHP is managed as an SPP by the online tester.

The online tester cannot be used to test a normal MHP (linked to the MCF-supplied library).