test(P3-1): 第56波 worker层更多引擎纯逻辑单测（+108）

- test_subtitle_render_engine.py: 53个（颜色转换/时间格式化/文字换行/ASS转义/样式）
- test_sticker_engine.py: 27个（配置类/位置解析/常量/便捷函数）
- test_tts_engine.py: 12个（数据类/入口判断/初始化）
- test_render_audio_utils.py: 16个（clip_effective_duration/RenderContext）

覆盖worker层4个模块的纯逻辑部分

tests/unit/test_render_audio_utils.py

@@ -0,0 +1,108 @@
+"""
+render_audio 纯工具函数测试.
+
+覆盖 clip_effective_duration / RenderContext 等纯逻辑.
+核心混音逻辑依赖 FFmpeg，由集成测试覆盖.
+"""
+
+from __future__ import annotations
+
+from pathlib import Path
+from types import SimpleNamespace
+from unittest.mock import MagicMock
+
+import pytest
+
+from video_processing.render_audio import RenderContext, clip_effective_duration
+
+
+class TestClipEffectiveDuration:
+    """clip_effective_duration 有效时长计算."""
+
+    def test_duration_specified_and_actual_longer(self):
+        """指定了 duration，且实际时长更长 → 取 duration"""
+        clip = SimpleNamespace(duration=5.0, actual_duration=10.0)
+        assert clip_effective_duration(clip) == 5.0
+
+    def test_duration_specified_and_actual_shorter(self):
+        """指定了 duration，但实际时长更短 → 取实际时长"""
+        clip = SimpleNamespace(duration=10.0, actual_duration=5.0)
+        assert clip_effective_duration(clip) == 5.0
+
+    def test_duration_specified_actual_zero(self):
+        """指定了 duration，但实际时长为 0 → 取 duration"""
+        clip = SimpleNamespace(duration=5.0, actual_duration=0.0)
+        assert clip_effective_duration(clip) == 5.0
+
+    def test_duration_specified_actual_negative(self):
+        """指定了 duration，但实际时长为负 → 取 duration"""
+        clip = SimpleNamespace(duration=5.0, actual_duration=-1.0)
+        assert clip_effective_duration(clip) == 5.0
+
+    def test_no_duration_use_actual(self):
+        """未指定 duration（0），用实际时长"""
+        clip = SimpleNamespace(duration=0.0, actual_duration=8.0)
+        assert clip_effective_duration(clip) == 8.0
+
+    def test_no_duration_negative_actual(self):
+        """未指定 duration，实际时长也为负 → 返回 0"""
+        clip = SimpleNamespace(duration=0.0, actual_duration=-5.0)
+        assert clip_effective_duration(clip) == 0.0
+
+    def test_no_duration_zero_actual(self):
+        """都为 0 → 返回 0"""
+        clip = SimpleNamespace(duration=0.0, actual_duration=0.0)
+        assert clip_effective_duration(clip) == 0.0
+
+    def test_negative_duration_use_actual(self):
+        """duration 为负（视为未指定），用实际时长"""
+        clip = SimpleNamespace(duration=-1.0, actual_duration=5.0)
+        assert clip_effective_duration(clip) == 5.0
+
+    def test_both_negative_returns_zero(self):
+        """两者都为负 → 返回 0"""
+        clip = SimpleNamespace(duration=-2.0, actual_duration=-3.0)
+        assert clip_effective_duration(clip) == 0.0
+
+    def test_exact_match(self):
+        """duration 与实际时长相等"""
+        clip = SimpleNamespace(duration=7.5, actual_duration=7.5)
+        assert clip_effective_duration(clip) == 7.5
+
+    def test_very_short_duration(self):
+        """很短的时长"""
+        clip = SimpleNamespace(duration=0.1, actual_duration=0.2)
+        assert clip_effective_duration(clip) == 0.1
+
+
+class TestRenderContext:
+    """RenderContext 渲染上下文."""
+
+    def test_create_with_work_dir_and_plan_id(self, tmp_path):
+        ctx = RenderContext(work_dir=tmp_path, plan_id="plan_123")
+        assert ctx.work_dir == tmp_path
+        assert ctx.plan_id == "plan_123"
+        assert ctx.noise_reduction_config is None
+        assert ctx._audio_cache == {}
+
+    def test_noise_reduction_config(self, tmp_path):
+        config = {"enabled": True, "strength": 0.5}
+        ctx = RenderContext(
+            work_dir=tmp_path,
+            plan_id="plan_123",
+            noise_reduction_config=config,
+        )
+        assert ctx.noise_reduction_config == config
+        assert ctx.noise_reduction_config["enabled"] is True
+
+    def test_audio_cache_isolation(self, tmp_path):
+        """每个实例有独立的缓存字典."""
+        ctx1 = RenderContext(work_dir=tmp_path, plan_id="p1")
+        ctx2 = RenderContext(work_dir=tmp_path, plan_id="p2")
+        ctx1._audio_cache["key1"] = True
+        assert "key1" not in ctx2._audio_cache
+        assert len(ctx2._audio_cache) == 0
+
+    def test_work_dir_path_type(self, tmp_path):
+        ctx = RenderContext(work_dir=tmp_path, plan_id="test")
+        assert isinstance(ctx.work_dir, Path)

tests/unit/test_sticker_engine.py

@@ -0,0 +1,285 @@
+"""
+贴纸引擎配置与纯逻辑测试.
+
+覆盖 ImageStickerConfig / TextStickerConfig / _resolve_position / 常量与便捷函数.
+引擎核心滤镜生成与渲染依赖 FFmpeg，由集成测试覆盖.
+"""
+
+from __future__ import annotations
+
+import pytest
+
+from video_processing.sticker_engine import (
+    POSITION_PRESETS,
+    STICKER_CATEGORIES,
+    ImageStickerConfig,
+    StickerEngine,
+    StickerOverlayResult,
+    TextStickerConfig,
+    get_sticker_categories,
+    parse_stickers_from_config,
+)
+
+
+class TestStickerConstants:
+    """常量测试."""
+
+    def test_nine_position_presets(self):
+        assert len(POSITION_PRESETS) == 9
+        assert "top_left" in POSITION_PRESETS
+        assert "top_center" in POSITION_PRESETS
+        assert "top_right" in POSITION_PRESETS
+        assert "center_left" in POSITION_PRESETS
+        assert "center" in POSITION_PRESETS
+        assert "center_right" in POSITION_PRESETS
+        assert "bottom_left" in POSITION_PRESETS
+        assert "bottom_center" in POSITION_PRESETS
+        assert "bottom_right" in POSITION_PRESETS
+
+    def test_position_values_are_fractions(self):
+        for name, (x, y) in POSITION_PRESETS.items():
+            assert 0.0 <= x <= 1.0, f"{name} x={x} out of range"
+            assert 0.0 <= y <= 1.0, f"{name} y={y} out of range"
+
+    def test_sticker_categories(self):
+        assert len(STICKER_CATEGORIES) >= 3
+        for cat_id, cat_name in STICKER_CATEGORIES:
+            assert isinstance(cat_id, str)
+            assert isinstance(cat_name, str)
+            assert len(cat_id) > 0
+            assert len(cat_name) > 0
+
+
+class TestImageStickerConfig:
+    """图片贴纸配置."""
+
+    def test_default_values(self):
+        cfg = ImageStickerConfig()
+        assert cfg.enabled is False
+        assert cfg.type == "image"
+        assert cfg.position == "top_right"
+        assert cfg.x is None
+        assert cfg.y is None
+        assert cfg.x_unit == "percent"
+        assert cfg.y_unit == "percent"
+        assert cfg.scale == 1.0
+        assert cfg.width is None
+        assert cfg.height is None
+        assert cfg.opacity == 1.0
+        assert cfg.start_time == 0.0
+        assert cfg.duration == 0.0
+        assert cfg.fade_in == 0.0
+        assert cfg.fade_out == 0.0
+        assert cfg.z_index == 10
+        assert cfg.image_url == ""
+        assert cfg.preset_id == ""
+
+    def test_custom_values(self):
+        cfg = ImageStickerConfig(
+            enabled=True,
+            position="center",
+            x=50.0,
+            y=30.0,
+            scale=0.5,
+            opacity=0.8,
+            start_time=1.0,
+            duration=5.0,
+            fade_in=0.5,
+            fade_out=0.5,
+            z_index=5,
+            image_url="/tmp/sticker.png",
+            preset_id="sticker_001",
+        )
+        assert cfg.enabled is True
+        assert cfg.position == "center"
+        assert cfg.x == 50.0
+        assert cfg.y == 30.0
+        assert cfg.scale == 0.5
+        assert cfg.opacity == 0.8
+        assert cfg.start_time == 1.0
+        assert cfg.duration == 5.0
+        assert cfg.z_index == 5
+        assert cfg.image_url == "/tmp/sticker.png"
+
+
+class TestTextStickerConfig:
+    """文字贴纸配置."""
+
+    def test_default_values(self):
+        cfg = TextStickerConfig()
+        assert cfg.enabled is False
+        assert cfg.type == "text"
+        assert cfg.text == ""
+        assert cfg.font_size == 36
+        assert cfg.font_color == "#FFFFFF"
+        assert cfg.font_family == "sans"
+        assert cfg.stroke_color == "#000000"
+        assert cfg.stroke_width == 2
+        assert cfg.shadow_color == "#000000"
+        assert cfg.shadow_x == 2
+        assert cfg.shadow_y == 2
+        assert cfg.shadow_alpha == 0.5
+        assert cfg.position == "center"
+        assert cfg.z_index == 10
+        assert cfg.bg_color == ""
+        assert cfg.bg_padding == 8
+        assert cfg.bg_alpha == 0.8
+        assert cfg.bg_corner_radius == 8
+
+    def test_custom_text_sticker(self):
+        cfg = TextStickerConfig(
+            enabled=True,
+            text="Hello",
+            font_size=48,
+            font_color="#FF0000",
+            position="bottom_center",
+            bg_color="#000000",
+            bg_padding=16,
+        )
+        assert cfg.enabled is True
+        assert cfg.text == "Hello"
+        assert cfg.font_size == 48
+        assert cfg.font_color == "#FF0000"
+        assert cfg.position == "bottom_center"
+        assert cfg.bg_color == "#000000"
+        assert cfg.bg_padding == 16
+
+
+class TestStickerOverlayResult:
+    """贴纸叠加结果."""
+
+    def test_default_values(self):
+        result = StickerOverlayResult(filter_str="overlay=10:20", output_label="[out]")
+        assert result.filter_str == "overlay=10:20"
+        assert result.output_label == "[out]"
+        assert result.extra_inputs == []
+
+    def test_with_extra_inputs(self):
+        result = StickerOverlayResult(
+            filter_str="overlay=0:0",
+            output_label="[out]",
+            extra_inputs=["/tmp/sticker.png"],
+        )
+        assert len(result.extra_inputs) == 1
+        assert result.extra_inputs[0] == "/tmp/sticker.png"
+
+
+class TestResolvePosition:
+    """_resolve_position 位置解析."""
+
+    def test_top_left_preset(self):
+        cfg = ImageStickerConfig(position="top_left")
+        x, y = StickerEngine._resolve_position(cfg, 1000, 500, 100, 50)
+        # top_left: (0.05, 0.05) → x = 0.05*1000 - 50 = 0, y = 0.05*500 - 25 = 0
+        assert x >= 0
+        assert y >= 0
+
+    def test_center_preset(self):
+        cfg = ImageStickerConfig(position="center")
+        x, y = StickerEngine._resolve_position(cfg, 1000, 500, 200, 100)
+        # center: (0.5, 0.5) → x = 500 - 100 = 400, y = 250 - 50 = 200
+        assert x == 400.0
+        assert y == 200.0
+
+    def test_bottom_right_preset(self):
+        cfg = ImageStickerConfig(position="bottom_right")
+        x, y = StickerEngine._resolve_position(cfg, 1000, 500, 100, 50)
+        # bottom_right: (0.95, 0.95) → x = 950 - 50 = 900, y = 475 - 25 = 450
+        assert x == 900.0
+        assert y == 450.0
+
+    def test_custom_percent_position(self):
+        cfg = ImageStickerConfig(position="center", x=25.0, y=75.0, x_unit="percent", y_unit="percent")
+        x, y = StickerEngine._resolve_position(cfg, 1000, 500, 100, 50)
+        # x = 0.25*1000 - 50 = 200, y = 0.75*500 - 25 = 350
+        assert x == 200.0
+        assert y == 350.0
+
+    def test_custom_pixel_position(self):
+        cfg = ImageStickerConfig(position="center", x=300, y=200, x_unit="pixel", y_unit="pixel")
+        x, y = StickerEngine._resolve_position(cfg, 1000, 500, 100, 50)
+        # x = 300/1000*1000 - 50 = 250, y = 200/500*500 - 25 = 175
+        # 等等，让我重新算：px = config.x / canvas_w = 300/1000 = 0.3
+        # x = px * canvas_w - sticker_w/2 = 0.3*1000 - 50 = 300 - 50 = 250
+        assert x == 250.0
+        assert y == 175.0
+
+    def test_zero_size_sticker(self):
+        cfg = ImageStickerConfig(position="center")
+        x, y = StickerEngine._resolve_position(cfg, 1000, 500, 0, 0)
+        # 贴纸尺寸为0时，位置就是中心点
+        assert x == 500.0
+        assert y == 250.0
+
+    def test_invalid_position_falls_back_to_center(self):
+        cfg = ImageStickerConfig(position="invalid_position")
+        x, y = StickerEngine._resolve_position(cfg, 1000, 500, 100, 50)
+        # 无效位置 → 默认居中 → x = 500 - 50 = 450, y = 250 - 25 = 225
+        assert x == 450.0
+        assert y == 225.0
+
+    def test_position_clamped_to_canvas(self):
+        # 贴纸太大，位置被钳制
+        cfg = ImageStickerConfig(position="top_left")
+        x, y = StickerEngine._resolve_position(cfg, 100, 100, 200, 200)
+        # 贴纸比画布还大，应该被钳制到 0
+        assert x >= 0
+        assert y >= 0
+        assert x <= 100
+        assert y <= 100
+
+    def test_zero_canvas_handling(self):
+        cfg = ImageStickerConfig(position="center", x=50, y=50, x_unit="pixel", y_unit="pixel")
+        x, y = StickerEngine._resolve_position(cfg, 0, 0, 10, 10)
+        # 画布为0时不应崩溃，结果被钳制到0
+        assert x == 0
+        assert y == 0
+
+    def test_text_sticker_position(self):
+        cfg = TextStickerConfig(position="top_right")
+        x, y = StickerEngine._resolve_position(cfg, 800, 400, 100, 30)
+        # top_right: (0.95, 0.05) → x = 760 - 50 = 710, 但被钳制到 canvas_w - sticker_w = 700
+        # y = 20 - 15 = 5
+        assert x == 700.0
+        assert y == 5.0
+
+
+class TestParseStickersFromConfig:
+    """parse_stickers_from_config 便捷函数."""
+
+    def test_none_returns_empty(self):
+        assert parse_stickers_from_config(None) == []
+
+    def test_empty_dict_returns_empty(self):
+        assert parse_stickers_from_config({}) == []
+
+    def test_no_stickers_key_returns_empty(self):
+        assert parse_stickers_from_config({"other": "data"}) == []
+
+    def test_stickers_list_returned(self):
+        stickers = [{"type": "image", "url": "/a.png"}, {"type": "text", "text": "hi"}]
+        result = parse_stickers_from_config({"stickers": stickers})
+        assert result == stickers
+        assert len(result) == 2
+
+    def test_stickers_not_a_list_returns_empty(self):
+        assert parse_stickers_from_config({"stickers": "not_a_list"}) == []
+
+    def test_empty_stickers_list(self):
+        assert parse_stickers_from_config({"stickers": []}) == []
+
+
+class TestGetStickerCategories:
+    """get_sticker_categories 便捷函数."""
+
+    def test_returns_list_of_tuples(self):
+        result = get_sticker_categories()
+        assert isinstance(result, list)
+        assert len(result) > 0
+        for item in result:
+            assert isinstance(item, tuple)
+            assert len(item) == 2
+
+    def test_matches_constant(self):
+        result = get_sticker_categories()
+        assert result == list(STICKER_CATEGORIES)

tests/unit/test_subtitle_render_engine.py

@@ -0,0 +1,299 @@
+"""
+字幕渲染引擎纯函数与配置测试.
+
+覆盖 SubtitleStyle / SubtitleSegment / 颜色转换 / 时间格式化 / 文字换行 / ASS转义等纯逻辑.
+引擎核心 render 方法依赖 FFmpeg，由集成测试覆盖.
+"""
+
+from __future__ import annotations
+
+import pytest
+
+from video_processing.subtitle_render_engine import (
+    SubtitleSegment,
+    SubtitleStyle,
+    _escape_ass_text,
+    _format_ass_time,
+    _hex_to_ass_bgr,
+    _hex_to_ass_color,
+    _opacity_to_ass_alpha,
+    _wrap_text,
+)
+
+
+class TestHexToAssColor:
+    """HEX → ASS 颜色转换."""
+
+    def test_white(self):
+        assert _hex_to_ass_color("#FFFFFF") == "&H00FFFFFF"
+
+    def test_black(self):
+        assert _hex_to_ass_color("#000000") == "&H00000000"
+
+    def test_red(self):
+        # #FF0000 → R=FF, G=00, B=00 → BGR=0000FF
+        assert _hex_to_ass_color("#FF0000") == "&H000000FF"
+
+    def test_blue(self):
+        # #0000FF → R=00, G=00, B=FF → BGR=FF0000
+        assert _hex_to_ass_color("#0000FF") == "&H00FF0000"
+
+    def test_green(self):
+        # #00FF00 → R=00, G=FF, B=00 → BGR=00FF00
+        assert _hex_to_ass_color("#00FF00") == "&H0000FF00"
+
+    def test_without_hash_prefix(self):
+        assert _hex_to_ass_color("FF0000") == "&H000000FF"
+
+    def test_lowercase_hex(self):
+        assert _hex_to_ass_color("#ff0000") == "&H000000FF"
+
+    def test_mixed_case(self):
+        assert _hex_to_ass_color("#aBcDeF") == "&H00EFCDAB"
+
+    def test_invalid_length_returns_default(self):
+        assert _hex_to_ass_color("#FFF") == "&H00FFFFFF"  # 3位
+        assert _hex_to_ass_color("#FF") == "&H00FFFFFF"   # 2位
+        assert _hex_to_ass_color("#") == "&H00FFFFFF"     # 空
+
+    def test_empty_string(self):
+        assert _hex_to_ass_color("") == "&H00FFFFFF"
+
+
+class TestHexToAssBgr:
+    """HEX → ASS BGR 部分."""
+
+    def test_white(self):
+        assert _hex_to_ass_bgr("#FFFFFF") == "FFFFFF"
+
+    def test_black(self):
+        assert _hex_to_ass_bgr("#000000") == "000000"
+
+    def test_red(self):
+        # #FF0000 → BGR = 0000FF
+        assert _hex_to_ass_bgr("#FF0000") == "0000FF"
+
+    def test_blue(self):
+        # #0000FF → BGR = FF0000
+        assert _hex_to_ass_bgr("#0000FF") == "FF0000"
+
+    def test_without_hash(self):
+        assert _hex_to_ass_bgr("FF0000") == "0000FF"
+
+    def test_invalid_length_returns_white(self):
+        assert _hex_to_ass_bgr("#123") == "FFFFFF"
+
+
+class TestOpacityToAssAlpha:
+    """不透明度 → ASS alpha."""
+
+    def test_fully_opaque(self):
+        # 1.0 → alpha = 255 - 255 = 0 → "00"
+        assert _opacity_to_ass_alpha(1.0) == "00"
+
+    def test_fully_transparent(self):
+        # 0.0 → alpha = 255 - 0 = 255 → "FF"
+        assert _opacity_to_ass_alpha(0.0) == "FF"
+
+    def test_half(self):
+        # 0.5 → alpha = 255 - 127 = 128 → "80" (因为 int(0.5*255)=127)
+        # 注意：int(0.5 * 255) = 127，255-127=128 → "80"
+        assert _opacity_to_ass_alpha(0.5) == "80"
+
+    def test_quarter(self):
+        # 0.25 → alpha = 255 - 63 = 192 → "C0"
+        assert _opacity_to_ass_alpha(0.25) == "C0"
+
+    def test_three_quarters(self):
+        # 0.75 → alpha = 255 - 191 = 64 → "40"
+        assert _opacity_to_ass_alpha(0.75) == "40"
+
+    def test_zero_padded(self):
+        # 结果始终是2位十六进制
+        result = _opacity_to_ass_alpha(1.0)
+        assert len(result) == 2
+        assert result == result.upper()
+
+
+class TestEscapeAssText:
+    """ASS 文本转义."""
+
+    def test_plain_text(self):
+        assert _escape_ass_text("hello world") == "hello world"
+
+    def test_newline_unix(self):
+        assert _escape_ass_text("line1\nline2") == "line1\\Nline2"
+
+    def test_newline_windows(self):
+        assert _escape_ass_text("line1\r\nline2") == "line1\\Nline2"
+
+    def test_newline_mac(self):
+        assert _escape_ass_text("line1\rline2") == "line1\\Nline2"
+
+    def test_curly_braces_replaced(self):
+        # ASS 中 {} 是样式标签，需要转义
+        assert _escape_ass_text("{text}") == "(text)"
+
+    def test_multiple_braces(self):
+        assert _escape_ass_text("{a}b{c}") == "(a)b(c)"
+
+    def test_mixed_special_chars(self):
+        text = "line1\n{bold}\nline3"
+        result = _escape_ass_text(text)
+        assert "\\N" in result
+        assert "(bold)" in result
+        assert "{" not in result
+        assert "}" not in result
+        assert "\n" not in result
+        assert "\r" not in result
+
+    def test_empty_string(self):
+        assert _escape_ass_text("") == ""
+
+
+class TestFormatAssTime:
+    """秒 → ASS 时间格式."""
+
+    def test_zero(self):
+        assert _format_ass_time(0.0) == "0:00:00.00"
+
+    def test_seconds_only(self):
+        assert _format_ass_time(5.5) == "0:00:05.50"
+
+    def test_minutes(self):
+        assert _format_ass_time(65.25) == "0:01:05.25"
+
+    def test_hours(self):
+        assert _format_ass_time(3661.5) == "1:01:01.50"
+
+    def test_exact_minute(self):
+        assert _format_ass_time(60.0) == "0:01:00.00"
+
+    def test_exact_hour(self):
+        assert _format_ass_time(3600.0) == "1:00:00.00"
+
+    def test_sub_second_precision(self):
+        # 两位小数（厘秒精度）
+        result = _format_ass_time(1.234)
+        # 1.234 秒 = 0:00:01.23（ASS 格式是两位小数/厘秒）
+        assert result.startswith("0:00:01.")
+        # 检查秒部分是两位小数格式
+        parts = result.split(":")
+        assert len(parts) == 3
+        sec_part = parts[2]
+        assert "." in sec_part
+        decimals = sec_part.split(".")[1]
+        assert len(decimals) == 2
+
+    def test_negative_returns_zero_hours(self):
+        # 负数也应该能处理（虽然业务上不应该出现）
+        result = _format_ass_time(-1.0)
+        # 至少不崩溃
+        assert isinstance(result, str)
+        assert ":" in result
+
+
+class TestWrapText:
+    """按字数换行."""
+
+    def test_short_text_no_wrap(self):
+        result = _wrap_text("短文本", 10)
+        assert result == ["短文本"]
+
+    def test_exact_length_no_wrap(self):
+        text = "一二三四五六七八九十"
+        result = _wrap_text(text, 10)
+        assert len(result) == 1
+        assert result[0] == text
+
+    def test_long_text_wraps(self):
+        text = "一二三四五六七八九十一二三四五六七八九十"
+        result = _wrap_text(text, 10)
+        assert len(result) == 2
+        assert len(result[0]) == 10
+        assert len(result[1]) == 10
+
+    def test_break_on_punctuation(self):
+        # 优先在标点处断开（标点在max_chars范围内靠前位置）
+        # 共12字，max=7，句号在第6位索引，range(7,3,-1)能扫到索引5的句号
+        text = "一二三四五。六七八九十一"
+        result = _wrap_text(text, 7)
+        assert result[0] == "一二三四五。"
+        assert result[1] == "六七八九十一"
+
+    def test_break_on_comma(self):
+        text = "一二三四五，六七八九十一"
+        result = _wrap_text(text, 7)
+        assert result[0] == "一二三四五，"
+        assert result[1] == "六七八九十一"
+
+    def test_multiple_lines(self):
+        text = "一二三四五六七八九十一二三四五六七八九十一二三四五"
+        result = _wrap_text(text, 10)
+        assert len(result) == 3
+        assert len(result[0]) == 10
+        assert len(result[1]) == 10
+        assert len(result[2]) == 5
+
+    def test_empty_string(self):
+        result = _wrap_text("", 10)
+        assert result == [""]
+
+    def test_max_chars_zero(self):
+        # 边界情况
+        text = "abc"
+        result = _wrap_text(text, 0)
+        # 0的话，max_chars//2也是0，range不会执行
+        # 按逻辑 len(text) > 0 成立，但 break_point 从 0 开始
+        # 这取决于具体实现，只要不崩溃就行
+        assert isinstance(result, list)
+        assert len(result) > 0
+
+    def test_punctuation_at_boundary(self):
+        # 标点刚好在 max_chars 位置
+        text = "一二三四五六七八九。"
+        result = _wrap_text(text, 10)
+        assert len(result) == 1  # 刚好10个字符（含标点）
+
+
+class TestSubtitleSegment:
+    """字幕片段数据类."""
+
+    def test_basic(self):
+        seg = SubtitleSegment(start=0.0, end=5.0, text="hello")
+        assert seg.start == 0.0
+        assert seg.end == 5.0
+        assert seg.text == "hello"
+
+    def test_duration(self):
+        seg = SubtitleSegment(start=1.5, end=4.5, text="test")
+        assert seg.end - seg.start == 3.0
+
+
+class TestSubtitleStyle:
+    """字幕样式配置."""
+
+    def test_default_values(self):
+        style = SubtitleStyle()
+        assert style.font_size > 0
+        assert isinstance(style.font_color, str)
+        assert isinstance(style.background_color, str)
+
+    def test_ass_color_generation(self):
+        style = SubtitleStyle(font_color="#FFFFFF")
+        # 应该能生成 ASS 颜色格式
+        color = style.ass_font_color
+        assert isinstance(color, str)
+        assert color.startswith("&H")
+
+    def test_ass_background_color(self):
+        style = SubtitleStyle(background_color="#000000", background_opacity=0.5)
+        color = style.ass_background_color
+        assert isinstance(color, str)
+        assert color.startswith("&H")
+
+    def test_opacity_affects_alpha(self):
+        style1 = SubtitleStyle(background_opacity=1.0)
+        style2 = SubtitleStyle(background_opacity=0.0)
+        # 不透明度不同，alpha 应该不同
+        assert style1.ass_background_color != style2.ass_background_color

tests/unit/test_tts_engine.py

@@ -0,0 +1,131 @@
+"""
+TTS 配音引擎数据类与纯逻辑测试.
+
+覆盖 VoiceoverSegment / VoiceoverResult / TtsEngine 入口判断等纯逻辑.
+TTS 合成调用依赖外部服务，由集成测试覆盖.
+"""
+
+from __future__ import annotations
+
+from pathlib import Path
+from unittest.mock import MagicMock
+
+import pytest
+
+from packages.domain.tts_config import TtsConfig
+from video_processing.tts_engine import TtsEngine, VoiceoverResult, VoiceoverSegment
+
+
+class TestVoiceoverSegment:
+    """配音片段数据类."""
+
+    def test_default_values(self):
+        seg = VoiceoverSegment(text="hello")
+        assert seg.text == "hello"
+        assert seg.start_time == 0.0
+        assert seg.end_time == 0.0
+        assert seg.audio_path is None
+        assert seg.duration == 0.0
+
+    def test_full_values(self):
+        seg = VoiceoverSegment(
+            text="hello world",
+            start_time=1.5,
+            end_time=3.0,
+            audio_path=Path("/tmp/test.wav"),
+            duration=1.5,
+        )
+        assert seg.text == "hello world"
+        assert seg.start_time == 1.5
+        assert seg.end_time == 3.0
+        assert seg.audio_path == Path("/tmp/test.wav")
+        assert seg.duration == 1.5
+
+    def test_duration_calculation(self):
+        seg = VoiceoverSegment(text="test", start_time=0.0, end_time=5.5)
+        assert seg.end_time - seg.start_time == 5.5
+
+
+class TestVoiceoverResult:
+    """配音结果数据类."""
+
+    def test_default_failure(self):
+        result = VoiceoverResult()
+        assert result.success is False
+        assert result.segments == []
+        assert result.total_duration == 0.0
+        assert result.error_message == ""
+
+    def test_success_result(self):
+        segs = [
+            VoiceoverSegment(text="hello", duration=1.0),
+            VoiceoverSegment(text="world", duration=2.0),
+        ]
+        result = VoiceoverResult(
+            success=True,
+            segments=segs,
+            total_duration=3.0,
+        )
+        assert result.success is True
+        assert len(result.segments) == 2
+        assert result.total_duration == 3.0
+        assert result.error_message == ""
+
+    def test_failure_with_message(self):
+        result = VoiceoverResult(success=False, error_message="TTS服务不可用")
+        assert result.success is False
+        assert result.error_message == "TTS服务不可用"
+
+    def test_segments_isolated_list(self):
+        """确保每个实例有独立的segments列表."""
+        r1 = VoiceoverResult()
+        r2 = VoiceoverResult()
+        r1.segments.append(VoiceoverSegment(text="test"))
+        assert len(r2.segments) == 0
+
+
+class TestTtsEngineInit:
+    """TTS 引擎初始化."""
+
+    def test_init_creates_work_dir(self, tmp_path):
+        mock_tts = MagicMock()
+        work_dir = tmp_path / "tts_work"
+        engine = TtsEngine(mock_tts, work_dir)
+        assert work_dir.exists()
+        assert work_dir.is_dir()
+
+    def test_init_with_existing_dir(self, tmp_path):
+        mock_tts = MagicMock()
+        work_dir = tmp_path / "existing"
+        work_dir.mkdir()
+        engine = TtsEngine(mock_tts, work_dir)
+        assert work_dir.exists()
+
+
+class TestTtsEngineEntryConditions:
+    """TTS 引擎入口判断逻辑（不调用真实 TTS）."""
+
+    def test_disabled_returns_failure(self, tmp_path):
+        mock_tts = MagicMock()
+        engine = TtsEngine(mock_tts, tmp_path)
+        config = TtsConfig(enabled=False, text="hello")
+        result = engine.generate_full_voiceover(config)
+        assert result.success is False
+        assert "未启用" in result.error_message or "空" in result.error_message
+        mock_tts.synthesize.assert_not_called()
+
+    def test_empty_text_returns_failure(self, tmp_path):
+        mock_tts = MagicMock()
+        engine = TtsEngine(mock_tts, tmp_path)
+        config = TtsConfig(enabled=True, text="")
+        result = engine.generate_full_voiceover(config)
+        assert result.success is False
+        mock_tts.synthesize.assert_not_called()
+
+    def test_whitespace_text_returns_failure(self, tmp_path):
+        mock_tts = MagicMock()
+        engine = TtsEngine(mock_tts, tmp_path)
+        config = TtsConfig(enabled=True, text="   ")
+        result = engine.generate_full_voiceover(config)
+        assert result.success is False
+        mock_tts.synthesize.assert_not_called()