A system and method for facilitating simulation of a computer program. A program representation is generated from a computer program. A simulation of the program is performed. Simulation may include applying heuristics to determine program flow for selected instructions, such as a branch instruction or a loop instruction. Simulation may also include creating imaginary objects as surrogates for real objects, when program code to create real objects is restricted, or fields of the objects are unavailable or uncertain, or for other reasons. Data descriptive of the simulation is inserted into the program representation. A visualizer may retrieve the program representation and generate a visualization that shows sequence flows resulting from the simulation.