tui-smoke-test

tui-smoke-test

A TUI needs a real TTY for raw mode + alt screen. A non-interactive shell (Claude Code's Bash, CI runner) doesn't have one, so calling the binary directly will either fail or hang. The script command on macOS/Linux provides a PTY and lets us drive the binary as if from a terminal.

This skill verifies liveness and cleanup, not correctness — it answers "does it open and close without breaking the user's shell?", not "are CPU values right?".

Build first

export PATH="$HOME/.cargo/bin:$PATH" && cargo build --release

(Debug builds work but cold-start is slower, which makes timing the q send fragile.)

Run it

(sleep 1.5; printf 'q') | script -q /tmp/rmon-smoke.log target/release/resource-monitor
echo "exit: $?"

The (sleep 1.5; printf 'q') lets the sampler fire at least once (≥1 second at default 1Hz) and renders ~10 frames before sending q over the PTY.

For a binary that takes flags (e.g. --config), pass them after the binary path:

(sleep 1.5; printf 'q') | script -q /tmp/rmon-smoke.log target/release/resource-monitor --debug

What to look for

Inspect /tmp/rmon-smoke.log:

• Exit code 0 (echoed after the pipe)
• Log contains both [?1049h (enter alt screen) and [?1049l (leave alt screen) — proves the cleanup path ran
• Log contains both [?25l (cursor hidden) and [?25h (cursor restored)
• After the run, your shell still echoes input normally (raw mode is off)

A quick check:

grep -q '\[?1049h' /tmp/rmon-smoke.log && grep -q '\[?1049l' /tmp/rmon-smoke.log && echo "alt-screen pair OK"

Common failures

• Exit code != 0 with no panic: tracing logs go to stderr → captured in the log. Read it.
• No ?1049l in log: the cleanup didn't run — likely an early return in App::run skipped leave_terminal, or the panic hook is restoring stdout but not the alt screen.
• Terminal stays broken after exit: the panic hook is missing or the process exited via SIGKILL (uncatchable). Confirm app::install_panic_hook is called before enter_terminal().
• q ignored, hangs until SIGINT: should_quit regressed, or event::poll is being given Duration::ZERO and never reading the key.
• script: command not found: macOS ships BSD script. On Linux: apt install bsdmainutils or util-linux.

Cleanup

rm -f /tmp/rmon-smoke.log

When NOT to use

• For runtime correctness (CPU% matches top, sparklines move under load) — that needs interactive verification by the user, or a --dump-style headless mode that prints metrics as JSON.
• For input that needs to be observed across multiple frames (typing in a search box, multi-key chord) — the simple printf pipeline can't model that. Use a real terminal for those flows.