Functional testing of computer programming code generated from an executable graphical model is performed. The model may include a plurality of graphical objects. The generated code may be stand-alone code, and may include a plurality of functions. A designation of one of the graphical objects may be received. The designated object has input/output defined graphically in the model. Meta-data mapping the designated object to one or more functions of the generated code may be created. The meta-data may also map the graphically defined input/output for the designated object to function input/output of the one or more functions of the generated code. A function interface may be generated using the meta-data that includes a call to the one or more functions, and the function input/output. During execution of the model, execution of the designated object is by-passed and the function interface and the portion of the generated code are executed.