trusty-mpm 1.7.3

//! Unit tests for trusty-mpm's tmux adapter (#2398/#3386/#5151), split out
//! of `tmux.rs` to keep that file under the 500-SLOC production cap (#610) —
//! the inline `mod tests` counted as production source.
//!
//! Every process-spawning test drives a scripted fake `tmux` binary written
//! to a temp dir, so none of them needs a live tmux server.

use super::*;

// ── #8233: the pane COMMAND-line length guard ──

#[test]
fn pane_command_limit_sits_below_max_canon() {
    // The tty's canonical-mode buffer is MAX_CANON = 1024 bytes on macOS
    // (`sys/syslimits.h:89`; `fpathconf(pty, _PC_MAX_CANON)` agrees). The guard
    // must sit below it with room for the terminating newline, and must not be
    // so low that the fixed-shape launch line (< 512 bytes) cannot pass.
    const {
        assert!(MAX_PANE_COMMAND_BYTES < 1024);
        assert!(MAX_PANE_COMMAND_BYTES >= 512);
    }
}

#[test]
fn oversized_pane_command_is_refused() {
    // The failure this exists for: 1054 bytes typed, ~1020 delivered, the rest
    // dropped by the kernel with nothing able to notice.
    let line = "x".repeat(MAX_PANE_COMMAND_BYTES + 1);
    let msg = refuse_oversized_pane_command(&line).expect("an over-length line must be refused");
    assert!(msg.contains("MAX_CANON"), "{msg}");
    assert!(
        msg.contains(&(MAX_PANE_COMMAND_BYTES + 1).to_string()),
        "{msg}"
    );
}

#[test]
fn pane_command_at_the_limit_is_allowed() {
    let line = "x".repeat(MAX_PANE_COMMAND_BYTES);
    assert!(refuse_oversized_pane_command(&line).is_none());
}

#[test]
fn send_command_line_refuses_an_oversized_line() {
    // Nothing is typed and nothing is spawned: the refusal happens before any
    // tmux process starts, so a bogus binary path proves no exec occurred.
    let line = "x".repeat(MAX_PANE_COMMAND_BYTES + 1);
    let err = send_command_line(
        Some("/nonexistent/definitely-not-tmux"),
        &TmuxTarget::session("tm-sess"),
        &line,
    )
    .expect_err("an over-length command must be refused");
    assert_eq!(err.kind(), std::io::ErrorKind::InvalidInput, "{err}");
    assert!(err.to_string().contains("#8233"), "{err}");
}

// ── #2414: untyped-argv builders for display-message / show-environment ──

#[test]
fn display_message_argv_untargeted() {
    assert_eq!(
        display_message_argv(None, "#S"),
        vec!["display-message", "-p", "#S"]
    );
}

#[test]
fn display_message_argv_session_targeted() {
    assert_eq!(
        display_message_argv(Some(&TmuxTarget::session("tmpm-sess")), "#{pane_pid}"),
        vec!["display-message", "-t", "=tmpm-sess:", "-p", "#{pane_pid}"]
    );
}

#[test]
fn show_environment_argv_untargeted() {
    assert_eq!(
        show_environment_argv(None, "TM_MANAGED_SESSION_ID"),
        vec!["show-environment", "TM_MANAGED_SESSION_ID"]
    );
}

#[test]
fn show_environment_argv_session_targeted() {
    assert_eq!(
        show_environment_argv(Some("tmpm-sess"), "TM_MANAGED_SESSION_ID"),
        vec![
            "show-environment",
            "-t",
            "=tmpm-sess",
            "TM_MANAGED_SESSION_ID"
        ]
    );
}

#[serial_test::serial]
#[test]
fn run_tmux_argv_with_bin_does_not_panic_on_missing_binary() {
    // Mirrors `run_tmux_with_bin_does_not_panic_on_missing_binary` for the
    // untyped-argv spawn path.
    let result = run_tmux_argv_with_bin(
        "definitely-not-a-real-tmux-binary-2414",
        &[
            "display-message".to_string(),
            "-p".to_string(),
            "#S".to_string(),
        ],
    );
    assert!(result.is_err());
}

#[test]
fn resolve_tmux_binary_does_not_panic() {
    // Works whether or not tmux is installed on the test host.
    let _ = resolve_tmux_binary();
}

#[test]
fn resolve_tmux_binary_or_bare_never_empty() {
    // Even when resolution fails entirely, the bare "tmux" fallback keeps
    // this non-empty — callers always get a spawnable binary name.
    assert!(!resolve_tmux_binary_or_bare().is_empty());
}

#[serial_test::serial]
#[test]
fn run_tmux_with_bin_does_not_panic_on_missing_binary() {
    // A deliberately bogus binary name must surface as an Err, never panic.
    let result = run_tmux_with_bin(
        "definitely-not-a-real-tmux-binary-2398",
        &TmuxCommand::ListSessions,
    );
    assert!(result.is_err());
}

#[serial_test::serial]
#[test]
fn create_managed_session_does_not_panic_on_missing_binary() {
    // Same smoke guarantee for the session-creation choke point: a bogus
    // binary must degrade to an Err (from the final new-session spawn),
    // never panic — including through the best-effort scrollback loop.
    let result = create_managed_session(
        Some("definitely-not-a-real-tmux-binary-2398"),
        "tmpm-test-2398-no-bin",
        None,
    );
    assert!(result.is_err());
}

#[test]
fn managed_session_command_sequence_matches_shared_layer() {
    // #3004 integration assertion: this crate's config-resolved
    // sequence must be EXACTLY what `trusty_common::tmux` would build
    // for `idempotent: true, command: None` (trusty-mpm's creation
    // semantics) with the same parameters — proving trusty-mpm's
    // session creation genuinely routes through the shared layer
    // rather than a local re-implementation drifting from it.
    let got = managed_session_command_sequence(
        "tmpm-sess",
        Some("/tmp/proj"),
        100_000,
        true,
        false,
        true,
    );
    let want = trusty_common::tmux::managed_session_commands(
        "tmpm-sess",
        Some("/tmp/proj"),
        100_000,
        true,
        false,
        true,
        None,
    );
    assert_eq!(got, want);
}

/// #3707: the exclusive create must not render `-A`, because `-A` is exactly
/// what turns a lost create race into two records sharing one pane.
#[test]
fn exclusive_command_sequence_omits_the_attach_flag() {
    let cmds =
        managed_session_command_sequence("tm-sess", Some("/tmp/p"), 100_000, true, false, false);
    let TmuxCommand::NewSession { idempotent, .. } = cmds.last().expect("ends with new-session")
    else {
        panic!("the sequence must end with NewSession");
    };
    assert!(!idempotent, "the exclusive create must not pass -A");
    let argv = trusty_common::tmux::tmux_argv(cmds.last().expect("ends with new-session"));
    assert!(
        !argv.contains(&"-A".to_string()),
        "argv still carries -A: {argv:?}"
    );
}

#[test]
fn managed_session_command_sequence_applies_options_before_new_session() {
    let cmds = managed_session_command_sequence("tmpm-sess", None, 50_000, false, false, true);
    assert_eq!(cmds.len(), 4);
    assert!(matches!(cmds[0], TmuxCommand::SetGlobalOption { .. }));
    assert!(matches!(cmds[1], TmuxCommand::SetGlobalOption { .. }));
    // #5151: the alternate-screen entry rides the same pre-new-session
    // path, at the WINDOW scope.
    assert!(matches!(cmds[2], TmuxCommand::SetWindowGlobalOption { .. }));
    assert!(matches!(cmds[3], TmuxCommand::NewSession { .. }));
}

// ── #3386: server-up confirmed before any `set-option -g` ───────────
//
// All of these drive a scripted fake `tmux` binary (a `#!/bin/sh` script
// written to a temp dir) rather than a live tmux server, so they are
// deterministic and safe to run anywhere `sh` exists.

/// Write an executable shell script at `dir/name` with body `body`,
/// returning its path as a `String` suitable for `create_managed_session`
/// / `run_tmux_with_bin`'s `bin` parameter.
///
/// #5391: the script is created already executable and the write handle is
/// dropped before it is returned, so no caller can exec it while this thread
/// still holds a writable fd — the same shape `trusty-agents`'
/// `test_env::write_executable_script` settled on for #1528. That closes the
/// self-inflicted half of the ETXTBSY race; the other half — a sibling
/// thread forking mid-write and handing its child an inherited copy of the
/// fd — is covered by the bounded retry in `core::spawn_disclaim`.
fn write_fake_tmux(dir: &std::path::Path, name: &str, body: &str) -> String {
    use std::io::Write as _;
    use std::os::unix::fs::OpenOptionsExt as _;

    let path = dir.join(name);
    {
        // `create_new` so the 0o755 mode is guaranteed to apply: `mode` is
        // honoured only when the open actually creates the file, and every
        // caller writes its script name once into its own temp dir.
        let mut f = std::fs::OpenOptions::new()
            .create_new(true)
            .write(true)
            .mode(0o755)
            .open(&path)
            .expect("create fake tmux script");
        f.write_all(body.as_bytes())
            .expect("write fake tmux script");
        // `f` drops here — the writable fd is closed before any exec.
    }
    path.to_string_lossy().into_owned()
}

#[serial_test::serial]
#[test]
fn ensure_server_up_retries_then_succeeds() {
    // Fails the first two `start-server` invocations (simulating the
    // #3386 window right after a dead server's socket dir is torn down),
    // then succeeds on the third — exactly `START_SERVER_MAX_ATTEMPTS`.
    let dir = tempfile::tempdir().unwrap();
    let counter = dir.path().join("attempts");
    std::fs::write(&counter, "0").unwrap();
    let script = format!(
        "#!/bin/sh\nn=$(cat '{counter}')\nn=$((n + 1))\necho \"$n\" > '{counter}'\nif [ \"$n\" -lt 3 ]; then\n  echo 'error connecting to socket (No such file or directory)' >&2\n  exit 1\nfi\nexit 0\n",
        counter = counter.display()
    );
    let bin = write_fake_tmux(dir.path(), "fake-tmux-retry", &script);

    let result = ensure_server_up(&bin);

    assert!(
        result.is_ok(),
        "must eventually succeed within {START_SERVER_MAX_ATTEMPTS} attempts: {result:?}"
    );
    assert_eq!(
        std::fs::read_to_string(&counter).unwrap().trim(),
        "3",
        "must have retried exactly up to the succeeding attempt"
    );
}

#[serial_test::serial]
#[test]
fn ensure_server_up_fails_loudly_after_exhausting_retries() {
    // Always fails — the probe must return a loud Err after exhausting
    // every attempt rather than silently reporting success.
    let dir = tempfile::tempdir().unwrap();
    let script =
        "#!/bin/sh\necho 'error connecting to socket (No such file or directory)' >&2\nexit 1\n";
    let bin = write_fake_tmux(dir.path(), "fake-tmux-always-fails", script);

    let result = ensure_server_up(&bin);

    assert!(
        result.is_err(),
        "an always-failing server probe must error loudly, never proceed as if it succeeded"
    );
    assert!(
        result.unwrap_err().contains("error connecting to socket"),
        "the Err must carry the underlying failure reason"
    );
}

#[serial_test::serial]
#[test]
fn probe_history_limit_reads_back_configured_value() {
    let dir = tempfile::tempdir().unwrap();
    let script = "#!/bin/sh\necho 100000\nexit 0\n";
    let bin = write_fake_tmux(dir.path(), "fake-tmux-show-options", script);

    assert_eq!(probe_history_limit(&bin), Ok(100_000));
}

#[serial_test::serial]
#[test]
fn probe_history_limit_errors_on_unparsable_output() {
    let dir = tempfile::tempdir().unwrap();
    let script = "#!/bin/sh\necho 'not-a-number'\nexit 0\n";
    let bin = write_fake_tmux(dir.path(), "fake-tmux-bad-output", script);

    let result = probe_history_limit(&bin);
    assert!(
        result.is_err(),
        "unparsable show-options output must error loudly, not silently pass verification"
    );
}

#[serial_test::serial]
#[test]
fn probe_history_limit_errors_on_nonzero_exit() {
    let dir = tempfile::tempdir().unwrap();
    let script = "#!/bin/sh\necho 'no server running' >&2\nexit 1\n";
    let bin = write_fake_tmux(dir.path(), "fake-tmux-show-options-fails", script);

    assert!(probe_history_limit(&bin).is_err());
}

// ── #5151: alternate-screen probe ───────────────────────────────────

/// A `show-options)` case body for a fake tmux that answers each probe
/// by OPTION NAME (`$4`), so the `history-limit` and `alternate-screen`
/// probes can be given different answers — the whole point of #5151 is
/// that they are separate options in separate scopes.
fn fake_show_options_case(history_limit: &str, alternate_screen: &str) -> String {
    format!(
        "  show-options)\n    case \"$4\" in\n      history-limit) echo {history_limit} ;;\n      alternate-screen) echo {alternate_screen} ;;\n    esac\n    ;;\n"
    )
}

#[serial_test::serial]
#[test]
fn probe_alternate_screen_reads_back_on() {
    let dir = tempfile::tempdir().unwrap();
    let bin = write_fake_tmux(
        dir.path(),
        "fake-tmux-alt-on",
        "#!/bin/sh\necho on\nexit 0\n",
    );
    assert_eq!(probe_alternate_screen(&bin), Ok(true));
}

#[serial_test::serial]
#[test]
fn probe_alternate_screen_reads_back_off() {
    let dir = tempfile::tempdir().unwrap();
    let bin = write_fake_tmux(
        dir.path(),
        "fake-tmux-alt-off",
        "#!/bin/sh\necho off\nexit 0\n",
    );
    assert_eq!(probe_alternate_screen(&bin), Ok(false));
}

#[serial_test::serial]
#[test]
fn probe_alternate_screen_errors_on_unrecognised_value() {
    // Anything tmux does not document must NOT be guessed at — a wrong
    // guess here is a silent pass on an option that did not land.
    let dir = tempfile::tempdir().unwrap();
    let bin = write_fake_tmux(
        dir.path(),
        "fake-tmux-alt-garbage",
        "#!/bin/sh\necho maybe\nexit 0\n",
    );
    assert!(probe_alternate_screen(&bin).is_err());
}

#[serial_test::serial]
#[test]
fn probe_alternate_screen_errors_on_nonzero_exit() {
    let dir = tempfile::tempdir().unwrap();
    let bin = write_fake_tmux(
        dir.path(),
        "fake-tmux-alt-fails",
        "#!/bin/sh\necho 'no server running' >&2\nexit 1\n",
    );
    assert!(probe_alternate_screen(&bin).is_err());
}

#[serial_test::serial]
#[test]
fn probe_alternate_screen_queries_the_window_scope() {
    // #5151 fail-open guard: the probe must read `-wg`, the same scope
    // `scrollback_option_commands` writes. Measured against live tmux
    // 3.6b, `set-option -pg alternate-screen off` exits 0, a `-pg`
    // readback reports "off", and the pane STILL enters the alternate
    // screen — a probe on any other scope would confirm nothing.
    let dir = tempfile::tempdir().unwrap();
    let log = dir.path().join("argv.log");
    let script = format!(
        "#!/bin/sh\necho \"$@\" >> '{log}'\necho off\nexit 0\n",
        log = log.display()
    );
    let bin = write_fake_tmux(dir.path(), "fake-tmux-alt-argv", &script);

    assert_eq!(probe_alternate_screen(&bin), Ok(false));
    assert_eq!(
        std::fs::read_to_string(&log).unwrap().trim(),
        "show-options -wg -v alternate-screen"
    );
}

#[serial_test::serial]
#[test]
fn create_managed_session_confirms_server_before_applying_options() {
    // #3386 end-to-end (still no live tmux): a fake `tmux` that records
    // each invocation's tmux sub-command (argv[0]) to a log file, always
    // succeeds, and echoes back the CONFIGURED history-limit for
    // `show-options` so the apply-and-verify cycle matches on its first
    // attempt. This exercises the EXACT choke point the
    // resume-after-server-death path (`SessionManager::resume` →
    // `resume_workdir::create_and_verify_pane` → `RealTmuxDriver::
    // create_session` → `TmuxDriver::create_session`) routes through, so
    // asserting the recorded order here proves the fix for that path too.
    //
    // #5040: the options are CONSTRUCTED here and injected, not resolved from
    // `~/.trusty-mpm/config.toml` on both sides. Reading the host config twice —
    // once here for the expectation, once inside `create_managed_session` for
    // the actual — let any concurrently-running test that redirects `$HOME`
    // answer the two reads from different environments, and this test failed
    // with no change to a single file it exercises. One value, passed in, cannot
    // diverge from itself.
    let dir = tempfile::tempdir().unwrap();
    let log = dir.path().join("calls.log");
    let opts = crate::core::trusty_tools_config::ResolvedTmuxOptions {
        history_limit: 123_456,
        mouse: true,
        alternate_screen: false,
    };
    let script = format!(
        "#!/bin/sh\necho \"$1\" >> '{log}'\ncase \"$1\" in\n{show_options}esac\nexit 0\n",
        log = log.display(),
        show_options = fake_show_options_case(
            &opts.history_limit.to_string(),
            if opts.alternate_screen { "on" } else { "off" },
        )
    );
    let bin = write_fake_tmux(dir.path(), "fake-tmux-order", &script);

    let outcome =
        create_managed_session_with_options(Some(&bin), "tmpm-3386-order-test", None, opts)
            .expect("fake tmux always exits 0");

    assert!(
        outcome.options_verified,
        "a fake tmux that echoes back the configured history-limit must verify successfully"
    );

    let calls = std::fs::read_to_string(&log).unwrap();
    let lines: Vec<&str> = calls.lines().collect();

    assert_eq!(
        lines.first(),
        Some(&"start-server"),
        "the server must be confirmed up BEFORE any set-option -g (#3386): {lines:?}"
    );
    let new_session_pos = lines
        .iter()
        .position(|l| *l == "new-session")
        .expect("new-session must still run");
    let set_option_positions: Vec<usize> = lines
        .iter()
        .enumerate()
        .filter(|(_, l)| **l == "set-option")
        .map(|(i, _)| i)
        .collect();
    assert!(
        !set_option_positions.is_empty(),
        "the scrollback/mouse options must still be applied: {lines:?}"
    );
    assert!(
        set_option_positions
            .iter()
            .all(|&p| p > 0 && p < new_session_pos),
        "set-option -g must run strictly AFTER start-server and BEFORE new-session \
         (#3386 / pre-existing #2398 ordering guarantee): {lines:?}"
    );
}

// ── #3386 review: apply-and-verify retries the WHOLE cycle ──────────

#[serial_test::serial]
#[test]
fn apply_and_verify_scrollback_options_succeeds_on_second_attempt() {
    // The probe reports the WRONG value on the first cycle, then the
    // correct value from the second cycle onward — the whole
    // apply-and-verify cycle (not just start-server) must retry and
    // eventually confirm success.
    let dir = tempfile::tempdir().unwrap();
    let counter = dir.path().join("probe-attempts");
    std::fs::write(&counter, "0").unwrap();
    let script = format!(
        "#!/bin/sh\ncase \"$1\" in\n  show-options)\n    case \"$4\" in\n      history-limit)\n        n=$(cat '{counter}')\n        n=$((n + 1))\n        echo \"$n\" > '{counter}'\n        if [ \"$n\" -lt 2 ]; then\n          echo 2000\n        else\n          echo 100000\n        fi\n        ;;\n      alternate-screen) echo on ;;\n    esac\n    ;;\nesac\nexit 0\n",
        counter = counter.display()
    );
    let bin = write_fake_tmux(dir.path(), "fake-tmux-verify-retry", &script);
    let options = trusty_common::tmux::scrollback_option_commands(100_000, true, true);

    let verified = apply_and_verify_scrollback_options(&bin, &options, 100_000, true);

    assert!(
        verified,
        "must succeed once the probe reports the expected value on a later attempt"
    );
    assert_eq!(
        std::fs::read_to_string(&counter).unwrap().trim(),
        "2",
        "must have retried the WHOLE cycle (not just start-server) exactly once"
    );
}

#[serial_test::serial]
#[test]
fn apply_and_verify_scrollback_options_returns_false_after_exhausting_retries() {
    // The probe ALWAYS reports the wrong value — every apply-and-verify
    // cycle must be attempted (never silently assumed to have worked),
    // and the function must return `false` (the caller-visible degraded
    // signal) rather than `true` once every attempt is exhausted.
    let dir = tempfile::tempdir().unwrap();
    let counter = dir.path().join("probe-attempts");
    std::fs::write(&counter, "0").unwrap();
    let script = format!(
        "#!/bin/sh\ncase \"$1\" in\n  show-options)\n    case \"$4\" in\n      history-limit)\n        n=$(cat '{counter}')\n        n=$((n + 1))\n        echo \"$n\" > '{counter}'\n        echo 2000\n        ;;\n      alternate-screen) echo on ;;\n    esac\n    ;;\nesac\nexit 0\n",
        counter = counter.display()
    );
    let bin = write_fake_tmux(dir.path(), "fake-tmux-verify-always-wrong", &script);
    let options = trusty_common::tmux::scrollback_option_commands(100_000, true, true);

    let verified = apply_and_verify_scrollback_options(&bin, &options, 100_000, true);

    assert!(
        !verified,
        "must return false (never silently proceed as verified) once every \
         apply-and-verify attempt is exhausted — this is the #3386 review's caller-visible \
         degraded signal"
    );
    assert_eq!(
        std::fs::read_to_string(&counter).unwrap().trim(),
        APPLY_VERIFY_MAX_ATTEMPTS.to_string(),
        "must have made exactly APPLY_VERIFY_MAX_ATTEMPTS probe attempts"
    );
}

// ── #5151: alternate-screen rides the same verified path ────────────

#[serial_test::serial]
#[test]
fn apply_and_verify_scrollback_options_fails_when_only_alternate_screen_is_wrong() {
    // #5151 regression: history-limit reads back correctly, but the
    // server reports `alternate-screen on` when `off` was configured —
    // exactly the shape a wrong-scope `set-option` produces. Verification
    // must fail. Before alternate-screen was probed at all this returned
    // `true`, reporting an ergonomics set that never landed.
    let dir = tempfile::tempdir().unwrap();
    let script = format!(
        "#!/bin/sh\ncase \"$1\" in\n{show_options}esac\nexit 0\n",
        show_options = fake_show_options_case("100000", "on")
    );
    let bin = write_fake_tmux(dir.path(), "fake-tmux-alt-mismatch", &script);
    let options = trusty_common::tmux::scrollback_option_commands(100_000, true, false);

    let verified = apply_and_verify_scrollback_options(&bin, &options, 100_000, false);

    assert!(
        !verified,
        "a correct history-limit must not verify away a wrong alternate-screen — that is \
         the fail-open #5151 exists to close"
    );
}

#[serial_test::serial]
#[test]
fn apply_and_verify_scrollback_options_verifies_alternate_screen_off() {
    // The positive counterpart: when the server DOES report the
    // configured `off`, the cycle verifies on its first attempt.
    let dir = tempfile::tempdir().unwrap();
    let script = format!(
        "#!/bin/sh\ncase \"$1\" in\n{show_options}esac\nexit 0\n",
        show_options = fake_show_options_case("100000", "off")
    );
    let bin = write_fake_tmux(dir.path(), "fake-tmux-alt-match", &script);
    let options = trusty_common::tmux::scrollback_option_commands(100_000, true, false);

    assert!(apply_and_verify_scrollback_options(
        &bin, &options, 100_000, false
    ));
}

#[serial_test::serial]
#[test]
fn apply_and_verify_probes_the_same_scope_it_sets() {
    // #5151 fail-open guard, asserted on the real argv the apply-and-
    // verify cycle emits: the `alternate-screen` set and its readback
    // must carry the SAME scope flag. A set at one scope verified by a
    // probe at another reports success for an option that did nothing.
    let dir = tempfile::tempdir().unwrap();
    let log = dir.path().join("argv.log");
    let script = format!(
        "#!/bin/sh\necho \"$@\" >> '{log}'\ncase \"$1\" in\n{show_options}esac\nexit 0\n",
        log = log.display(),
        show_options = fake_show_options_case("100000", "off")
    );
    let bin = write_fake_tmux(dir.path(), "fake-tmux-scope-log", &script);
    let options = trusty_common::tmux::scrollback_option_commands(100_000, true, false);

    assert!(apply_and_verify_scrollback_options(
        &bin, &options, 100_000, false
    ));

    let calls = std::fs::read_to_string(&log).unwrap();
    let scope_of = |prefix: &str| -> String {
        let line = calls
            .lines()
            .find(|l| l.starts_with(prefix) && l.contains("alternate-screen"))
            .unwrap_or_else(|| panic!("no {prefix} call for alternate-screen in: {calls}"));
        line.split_whitespace()
            .nth(1)
            .expect("scope flag")
            .to_string()
    };

    let set_scope = scope_of("set-option");
    let show_scope = scope_of("show-options");
    assert_eq!(set_scope, "-wg", "alternate-screen must be set at -wg");
    assert_eq!(
        show_scope, set_scope,
        "the readback must query the scope the set wrote: {calls}"
    );
}

// ── #6529: the tmux client's UTF-8 declaration decides whether tmux keeps
// the delimiters in a `-F` listing ────────────────────────────────────────

/// tmux reads ONE locale variable, by precedence — mirror that, not any-of.
///
/// Why: `LC_ALL=C` beside `LANG=en_US.UTF-8` is the case an any-of test gets
/// backwards. tmux takes the first non-empty of `LC_ALL`, `LC_CTYPE`, `LANG`
/// and tests only that one, so that environment is NOT UTF-8 to tmux and its
/// server sanitizes the tabs out of the reply.
/// What: pins each precedence step and the empty-value skip.
/// Test: this is the test.
#[test]
fn env_declares_utf8_follows_tmux_precedence() {
    assert!(declares_utf8(Some("en_US.UTF-8"), None, None));
    assert!(declares_utf8(Some("C.utf8"), None, None));
    assert!(!declares_utf8(Some("C"), None, None));
    assert!(!declares_utf8(Some("POSIX"), None, Some("en_US.UTF-8")));
    // An empty value is skipped, exactly as tmux's `*s == '\0'` test does.
    assert!(declares_utf8(Some(""), None, Some("en_US.UTF-8")));
    assert!(declares_utf8(None, Some("en_US.UTF-8"), Some("C")));
    // Nothing set at all — the environment launchd hands the daemon (#6529).
    assert!(!declares_utf8(None, None, None));
}

/// The helper injects `LC_ALL` only when the inherited environment needs it.
///
/// Why: overriding an operator's own UTF-8 locale is a behaviour change this
/// fix does not need. The injection exists for an environment that declares
/// nothing, which is what launchd hands the daemon.
/// What: builds a `Command` under this process's real environment and asserts
/// the helper's decision agrees with [`declares_utf8`] for that environment,
/// mutating no process-global state.
/// Test: this is the test.
#[test]
fn force_utf8_client_env_is_a_no_op_under_a_utf8_locale() {
    let read = |key: &str| std::env::var(key).ok();
    let already = declares_utf8(
        read("LC_ALL").as_deref(),
        read("LC_CTYPE").as_deref(),
        read("LANG").as_deref(),
    );
    let mut cmd = std::process::Command::new("true");
    force_utf8_client_env(&mut cmd);
    let injected = cmd
        .get_envs()
        .any(|(k, v)| k == "LC_ALL" && v == Some(std::ffi::OsStr::new(UTF8_LOCALE)));
    assert_eq!(
        injected, !already,
        "LC_ALL must be injected exactly when the environment does not already \
         declare UTF-8 (#6529)"
    );
}