Running the same model under PathSim and under FastSim, without changing it.

Turning a block diagram into standalone C99, and proving the C still solves the same problem.

Finding a limit cycle directly, instead of integrating until the transient has died away.

Compiling a hand-written NumPy function to native Rust, and getting its exact Jacobian with it.

Writing a model out as a Functional Mock-up Unit, for both interface types, and packaging a subsystem as a reusable component.

Running Functional Mock-up Units as FastSim blocks, in both interface types.