test: add focused playback helper unit coverage

tests/playback/test_playback_process_helpers.py

@@ -0,0 +1,67 @@
+from __future__ import annotations
+
+import subprocess
+from pathlib import Path
+
+from auditui.playback import process as process_mod
+
+
+class DummyProc:
+    """Minimal subprocess-like object for terminate_process tests."""
+
+    def __init__(self, alive: bool = True) -> None:
+        """Initialize process state and bookkeeping flags."""
+        self._alive = alive
+        self.terminated = False
+        self.killed = False
+        self.pid = 123
+
+    def poll(self) -> int | None:
+        """Return None while process is alive and 0 when stopped."""
+        return None if self._alive else 0
+
+    def terminate(self) -> None:
+        """Mark process as terminated and no longer alive."""
+        self.terminated = True
+        self._alive = False
+
+    def wait(self, timeout: float | None = None) -> int:
+        """Return immediately to emulate a cooperative shutdown."""
+        del timeout
+        return 0
+
+    def kill(self) -> None:
+        """Mark process as killed and no longer alive."""
+        self.killed = True
+        self._alive = False
+
+
+def test_build_ffplay_cmd_includes_activation_seek_and_speed() -> None:
+    """Ensure ffplay command includes optional playback arguments when set."""
+    cmd = process_mod.build_ffplay_cmd(Path("book.aax"), "abcd", 12.5, 1.2)
+    assert "-activation_bytes" in cmd
+    assert "-ss" in cmd
+    assert "atempo=1.20" in " ".join(cmd)
+
+
+def test_terminate_process_handles_alive_process() -> None:
+    """Ensure terminate_process gracefully shuts down a running process."""
+    proc = DummyProc(alive=True)
+    process_mod.terminate_process(proc)  # type: ignore[arg-type]
+    assert proc.terminated is True
+
+
+def test_run_ffplay_returns_none_when_unavailable(monkeypatch) -> None:
+    """Ensure ffplay launch exits early when binary is not on PATH."""
+    monkeypatch.setattr(process_mod, "is_ffplay_available", lambda: False)
+    assert process_mod.run_ffplay(["ffplay", "book.aax"]) == (None, None)
+
+
+def test_send_signal_delegates_to_os_kill(monkeypatch) -> None:
+    """Ensure send_signal forwards process PID and signal to os.kill."""
+    seen: list[tuple[int, object]] = []
+    monkeypatch.setattr(
+        process_mod.os, "kill", lambda pid, sig: seen.append((pid, sig))
+    )
+    process_mod.send_signal(DummyProc(), process_mod.signal.SIGSTOP)  # type: ignore[arg-type]
+    assert seen and seen[0][0] == 123