fix(test): 修复tts_segment_synthesis单测mock路径，适配audio_merger下沉run_ffmpeg

tests/unit/test_tts_segment_synthesis.py

@@ -107,10 +107,11 @@ class TestAudioMerger:
         finally:
             os.unlink(path)
 
-    @patch("packages.application.tts_job.audio_merger.subprocess.run")
-    def test_ffmpeg_called_correctly(self, mock_run: MagicMock) -> None:
-        """多文件调用 FFmpeg concat。"""
-        mock_run.return_value = MagicMock(returncode=0)
+    @patch("packages.application.tts_job.audio_merger.run_ffmpeg")
+    def test_ffmpeg_called_correctly(self, mock_run_ffmpeg: MagicMock) -> None:
+        """多文件调用 FFmpeg concat（通过 run_ffmpeg 统一入口）。"""
+        # run_ffmpeg 成功返回 (stdout, stderr)
+        mock_run_ffmpeg.return_value = ("", "")
 
         # 创建临时文件
         paths = []
@@ -130,20 +131,24 @@ class TestAudioMerger:
                 except (FileNotFoundError, OSError):
                     pass  # Expected since we're mocking
 
-            # 验证 FFmpeg 被调用
-            mock_run.assert_called_once()
-            cmd = mock_run.call_args[0][0]
-            assert cmd[0] == "ffmpeg"
+            # 验证 run_ffmpeg 被调用
+            mock_run_ffmpeg.assert_called_once()
+            cmd = mock_run_ffmpeg.call_args[0][0]
+            from shared.ffmpeg_utils import FFMPEG_BIN
+
+            assert cmd[0] == FFMPEG_BIN
             assert "-f" in cmd
             assert "concat" in cmd
         finally:
             for p in paths:
                 os.unlink(p)
 
-    @patch("packages.application.tts_job.audio_merger.subprocess.run")
-    def test_ffmpeg_failure_raises(self, mock_run: MagicMock) -> None:
-        """FFmpeg 失败抛出 AudioMergeError。"""
-        mock_run.return_value = MagicMock(returncode=1, stderr="error details")
+    @patch("packages.application.tts_job.audio_merger.run_ffmpeg")
+    def test_ffmpeg_failure_raises(self, mock_run_ffmpeg: MagicMock) -> None:
+        """FFmpeg 失败抛出 AudioMergeError（通过 run_ffmpeg 抛出 CalledProcessError）。"""
+        from subprocess import CalledProcessError
+
+        mock_run_ffmpeg.side_effect = CalledProcessError(returncode=1, cmd=["ffmpeg"], stderr="error details")
 
         paths = []
         for i in range(2):
@@ -155,6 +160,7 @@ class TestAudioMerger:
             merger = AudioMerger()
             with pytest.raises(AudioMergeError, match="FFmpeg 合并失败"):
                 merger.merge(paths)
+            mock_run_ffmpeg.assert_called_once()
         finally:
             for p in paths:
                 os.unlink(p)