Tests test_no_server_* and test_raise_if_dead_no_server_raises fail when stale tmux daemon exists at hardcoded socket name

[tony]

Summary

Three tests in tests/test_server.py fail when a tmux server happens to be alive at the exact socket path they hardcode. Because the tests register no cleanup, any daemon that ends up at one of those socket names — from a prior crashed run, manual debugging, or anything else — sticks around and breaks them on every subsequent run, even in isolation.

The library code (Server.is_alive, Server.cmd, Server.raise_if_dead, tmux_cmd) is correct. This is purely a test-isolation defect.

Affected tests (tests/test_server.py)

def test_no_server_sessions() -> None:
    server = Server(socket_name="test_attached_session_no_server")
    assert server.sessions == []

def test_no_server_attached_sessions() -> None:
    server = Server(socket_name="test_no_server_attached_sessions")
    assert server.attached_sessions == []

def test_no_server_is_alive() -> None:
    dead_server = Server(socket_name="test_no_server_is_alive")
    assert not dead_server.is_alive()

def test_raise_if_dead_no_server_raises() -> None:
    dead_server = Server(socket_name="test_attached_session_no_server")
    with pytest.raises(subprocess.CalledProcessError):
        dead_server.raise_if_dead()

(Note: test_no_server_sessions and test_raise_if_dead_no_server_raises share the same hardcoded socket name test_attached_session_no_server — a copy-paste leftover that matches neither function name.)

Reproduction

$ tmux -L test_no_server_is_alive new-session -d
$ uv run pytest tests/test_server.py::test_no_server_is_alive -v

Result:

tests/test_server.py:210: in test_no_server_is_alive
    assert not dead_server.is_alive()
E   assert not True

Same pattern reproduces for the other two:

$ tmux -L test_attached_session_no_server new-session -d
$ uv run pytest tests/test_server.py::test_no_server_sessions tests/test_server.py::test_raise_if_dead_no_server_raises

Root cause

• The tests construct Server with hardcoded socket_name strings.
• They register no finalizer, so anything that creates a daemon at /tmp/tmux-<uid>/<socket_name> persists indefinitely.
• tmux does not always unlink(2) its socket on non-graceful exit, so leftover socket files accumulate in /tmp/tmux-<uid>/.
• A later test run's Server(socket_name=...).is_alive() correctly reports True because the daemon really is alive — the test's assumption that the name is unused is the wrong premise.

In my environment two such daemons had been listening since 3 days prior, with PIDs 984553 and 984791, on /tmp/tmux-1000/test_attached_session_no_server and /tmp/tmux-1000/test_no_server_is_alive respectively. lsof -U | grep tmux confirmed live LISTEN sockets on both paths.

Proposed fix

Use the existing server fixture (src/libtmux/pytest_plugin.py:144-182) — it already produces a Server with a unique random socket name (libtmux_test{N}) and registers a _reap_test_server finalizer that kills any daemon and unlinks the socket file. A freshly-created Server with a unique name has no daemon running on it, so it is the "dead server" these tests need.

def test_no_server_sessions(server: Server) -> None:
    assert server.sessions == []

def test_no_server_attached_sessions(server: Server) -> None:
    assert server.attached_sessions == []

def test_no_server_is_alive(server: Server) -> None:
    assert not server.is_alive()

def test_raise_if_dead_no_server_raises(server: Server) -> None:
    with pytest.raises(subprocess.CalledProcessError):
        server.raise_if_dead()

This eliminates every hardcoded socket name, removes the typo coupling, and inherits cleanup automatically.

Workaround for affected users

$ tmux -L test_attached_session_no_server kill-server 2>/dev/null
$ tmux -L test_no_server_is_alive kill-server 2>/dev/null
$ tmux -L test_no_server_attached_sessions kill-server 2>/dev/null
$ rm -f /tmp/tmux-$(id -u)/{test_attached_session_no_server,test_no_server_is_alive,test_no_server_attached_sessions}

Environment

• libtmux: master @ 4e19628 ("py(deps[dev]) Bump dev packages")
• Python 3.10+
• tmux: system tmux on Linux 6.6.87.2-microsoft-standard-WSL2