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7.5 Beyond screenshots

Screenshots are the general-purpose check, but they are not the only one.

  • --magic-port turns a chosen I/O port into a debug channel: your program writes to it, JNEXT prints to stderr. With --magic-port-mode line it buffers until a CR/LF, which makes it a printf your test can grep. JNEXT uses exactly this in test/00regression/scripts/magic-port-func.sh.
  • --magic-breakpoint lets a program halt the emulator from inside itself (see chapter 6).
  • --delayed-snapshot saves machine state rather than a picture, at a frame you choose — useful when what you want to assert is memory, not pixels.
  • --wav-record captures the mixed audio, including headless, so a sound change can be regression-tested too.
  • RZX (--rzx-record / --rzx-play) replays a whole recorded session input-for-input.

The full option list is in jnext(1).