diff --git a/tests/unit/test_chroma_key_engine.py b/tests/unit/test_chroma_key_engine.py
new file mode 100755
index 000000000..d84bd0948
--- /dev/null
+++ b/tests/unit/test_chroma_key_engine.py
@@ -0,0 +1,189 @@
+"""绿幕抠像引擎单元测试 - 配置解析等纯逻辑."""
+
+from __future__ import annotations
+
+import pytest
+
+from video_processing.chroma_key_engine import (
+    CHROMA_KEY_PRESETS,
+    ChromaKeyConfig,
+)
+
+
+class TestChromaKeyConfigDefaults:
+    """默认配置测试."""
+
+    def test_default_values(self):
+        """默认值正确."""
+        config = ChromaKeyConfig()
+        assert config.enabled is False
+        assert config.key_color == "#00FF00"
+        assert config.similarity == 0.3
+        assert config.blend == 0.1
+        assert config.spill_suppress == 0.0
+
+
+class TestChromaKeyConfigFromDict:
+    """from_dict 配置解析测试."""
+
+    def test_none_returns_disabled(self):
+        """None 返回禁用配置."""
+        config = ChromaKeyConfig.from_dict(None)
+        assert config.enabled is False
+
+    def test_empty_dict_returns_disabled(self):
+        """空字典返回禁用."""
+        config = ChromaKeyConfig.from_dict({})
+        assert config.enabled is False
+
+    def test_disabled_returns_disabled(self):
+        """enabled=False 返回禁用."""
+        config = ChromaKeyConfig.from_dict({"enabled": False})
+        assert config.enabled is False
+
+    def test_enabled_default_values(self):
+        """启用时使用默认参数."""
+        config = ChromaKeyConfig.from_dict({"enabled": True})
+        assert config.enabled is True
+        assert config.key_color == "#00FF00"
+        assert config.similarity == 0.3
+        assert config.blend == 0.1
+        assert config.spill_suppress == 0.0
+
+    def test_custom_key_color(self):
+        """自定义抠像颜色."""
+        config = ChromaKeyConfig.from_dict({
+            "enabled": True,
+            "key_color": "#0000FF",
+        })
+        assert config.key_color == "#0000FF"
+
+    def test_similarity_parsed(self):
+        """相似度解析."""
+        config = ChromaKeyConfig.from_dict({
+            "enabled": True,
+            "similarity": 0.5,
+        })
+        assert config.similarity == 0.5
+
+    def test_similarity_clamped_min(self):
+        """相似度下限钳制."""
+        config = ChromaKeyConfig.from_dict({
+            "enabled": True,
+            "similarity": 0.001,
+        })
+        assert config.similarity == 0.01
+
+    def test_similarity_clamped_max(self):
+        """相似度上限钳制."""
+        config = ChromaKeyConfig.from_dict({
+            "enabled": True,
+            "similarity": 2.0,
+        })
+        assert config.similarity == 1.0
+
+    def test_blend_clamped_min(self):
+        """混合度下限钳制."""
+        config = ChromaKeyConfig.from_dict({
+            "enabled": True,
+            "blend": -0.5,
+        })
+        assert config.blend == 0.0
+
+    def test_blend_clamped_max(self):
+        """混合度上限钳制."""
+        config = ChromaKeyConfig.from_dict({
+            "enabled": True,
+            "blend": 1.5,
+        })
+        assert config.blend == 1.0
+
+    def test_spill_suppress_clamped(self):
+        """溢色抑制钳制."""
+        config = ChromaKeyConfig.from_dict({
+            "enabled": True,
+            "spill_suppress": 2.0,
+        })
+        assert config.spill_suppress == 1.0
+
+    def test_invalid_similarity_falls_back(self):
+        """无效相似度回退到默认."""
+        config = ChromaKeyConfig.from_dict({
+            "enabled": True,
+            "similarity": "not_a_number",
+        })
+        assert config.similarity == 0.3
+
+    def test_invalid_blend_falls_back(self):
+        """无效混合度回退."""
+        config = ChromaKeyConfig.from_dict({
+            "enabled": True,
+            "blend": "high",
+        })
+        assert config.blend == 0.1
+
+    def test_key_color_stripped(self):
+        """颜色值去除首尾空格."""
+        config = ChromaKeyConfig.from_dict({
+            "enabled": True,
+            "key_color": "  #FF0000  ",
+        })
+        assert config.key_color == "#FF0000"
+
+    def test_all_params_custom(self):
+        """所有参数自定义."""
+        config = ChromaKeyConfig.from_dict({
+            "enabled": True,
+            "key_color": "#0000FF",
+            "similarity": 0.45,
+            "blend": 0.15,
+            "spill_suppress": 0.6,
+        })
+        assert config.enabled is True
+        assert config.key_color == "#0000FF"
+        assert config.similarity == 0.45
+        assert config.blend == 0.15
+        assert config.spill_suppress == 0.6
+
+
+class TestHasEffect:
+    """has_effect 方法测试."""
+
+    def test_disabled_no_effect(self):
+        """禁用时无效果."""
+        config = ChromaKeyConfig(enabled=False)
+        assert config.has_effect() is False
+
+    def test_enabled_with_similarity_has_effect(self):
+        """启用且有相似度时有效果."""
+        config = ChromaKeyConfig(enabled=True, similarity=0.3)
+        assert config.has_effect() is True
+
+    def test_zero_similarity_no_effect(self):
+        """相似度为0时无效果."""
+        config = ChromaKeyConfig(enabled=True, similarity=0.0)
+        assert config.has_effect() is False
+
+
+class TestChromaKeyPresets:
+    """预设配置测试."""
+
+    def test_five_presets(self):
+        """5个预设."""
+        assert len(CHROMA_KEY_PRESETS) == 5
+
+    def test_preset_names(self):
+        """预设名称正确."""
+        assert "green_screen" in CHROMA_KEY_PRESETS
+        assert "blue_screen" in CHROMA_KEY_PRESETS
+        assert "red_screen" in CHROMA_KEY_PRESETS
+        assert "precise_green" in CHROMA_KEY_PRESETS
+        assert "soft_green" in CHROMA_KEY_PRESETS
+
+    def test_presets_have_required_keys(self):
+        """每个预设包含必要字段."""
+        for name, preset in CHROMA_KEY_PRESETS.items():
+            assert "key_color" in preset, f"{name} missing key_color"
+            assert "similarity" in preset, f"{name} missing similarity"
+            assert "blend" in preset, f"{name} missing blend"
+            assert "spill_suppress" in preset, f"{name} missing spill_suppress"
diff --git a/tests/unit/test_color_grade_engine.py b/tests/unit/test_color_grade_engine.py
index a3503f266..f7e2bbde3 100755
--- a/tests/unit/test_color_grade_engine.py
+++ b/tests/unit/test_color_grade_engine.py
@@ -1,97 +1,25 @@
-"""滤镜调色引擎单元测试."""
+"""调色引擎单元测试 - 配置解析等纯逻辑."""
 
 from __future__ import annotations
 
 import pytest
+
 from video_processing.color_grade_engine import (
     DEFAULT_PARAMS,
     PARAM_RANGES,
-    PRESET_BW,
-    PRESET_CINEMA,
-    PRESET_COOL,
-    PRESET_DISPLAY_NAMES,
-    PRESET_FILM,
-    PRESET_FRESH,
-    PRESET_JAPANESE,
     PRESET_PARAMS,
-    PRESET_VINTAGE,
-    PRESET_WARM,
+    VALID_PRESETS,
     ColorGradeConfig,
-    ColorGradeEngine,
-    get_preset_names,
-    get_preset_params,
 )
 
-# ── 预设常量测试 ──────────────────────────────────────────────────────────────
 
+class TestColorGradeConfigDefaults:
+    """默认配置测试."""
 
-class TestPresetConstants:
-    """预设常量完整性测试."""
-
-    def test_eight_presets_defined(self):
-        """应该有8种预设."""
-        assert len(PRESET_PARAMS) == 8
-        assert len(PRESET_DISPLAY_NAMES) == 8
-
-    def test_all_presets_have_display_names(self):
-        """每个预设都应该有中文显示名."""
-        for key in PRESET_PARAMS:
-            assert key in PRESET_DISPLAY_NAMES
-            assert PRESET_DISPLAY_NAMES[key]  # 非空
-
-    def test_preset_params_have_all_keys(self):
-        """每个预设应该包含所有5个参数."""
-        required_keys = {"brightness", "contrast", "saturation", "temperature", "hue"}
-        for key, params in PRESET_PARAMS.items():
-            assert required_keys.issubset(params.keys()), f"预设 {key} 缺少参数"
-
-    def test_preset_params_in_valid_range(self):
-        """所有预设参数应该在合法范围内."""
-        for preset_name, params in PRESET_PARAMS.items():
-            for param_name, value in params.items():
-                min_val, max_val = PARAM_RANGES[param_name]
-                assert (
-                    min_val <= value <= max_val
-                ), f"预设 {preset_name} 的 {param_name}={value} 超出范围 [{min_val}, {max_val}]"
-
-    def test_black_white_has_zero_saturation(self):
-        """黑白预设饱和度应该为0."""
-        assert PRESET_PARAMS[PRESET_BW]["saturation"] == 0
-
-    def test_warm_preset_has_positive_temperature(self):
-        """暖色预设色温应该为正."""
-        assert PRESET_PARAMS[PRESET_WARM]["temperature"] > 0
-
-    def test_cool_preset_has_negative_temperature(self):
-        """冷色预设色温应该为负."""
-        assert PRESET_PARAMS[PRESET_COOL]["temperature"] < 0
-
-
-# ── ColorGradeConfig.from_dict 测试 ───────────────────────────────────────────
-
-
-class TestColorGradeConfigFromDict:
-    """配置字典解析测试."""
-
-    def test_none_config(self):
-        """None返回disabled."""
-        config = ColorGradeConfig.from_dict(None)
-        assert not config.enabled
-
-    def test_empty_dict(self):
-        """空字典返回disabled."""
-        config = ColorGradeConfig.from_dict({})
-        assert not config.enabled
-
-    def test_enabled_false(self):
-        """enabled=False返回disabled."""
-        config = ColorGradeConfig.from_dict({"enabled": False})
-        assert not config.enabled
-
-    def test_enabled_only(self):
-        """只开enabled，无预设无自定义参数."""
-        config = ColorGradeConfig.from_dict({"enabled": True})
-        assert config.enabled
+    def test_default_values(self):
+        """默认值正确."""
+        config = ColorGradeConfig()
+        assert config.enabled is False
         assert config.preset == ""
         assert config.brightness is None
         assert config.contrast is None
@@ -99,474 +27,226 @@ class TestColorGradeConfigFromDict:
         assert config.temperature is None
         assert config.hue is None
 
-    def test_with_preset(self):
-        """指定预设."""
-        config = ColorGradeConfig.from_dict({"enabled": True, "preset": PRESET_FRESH})
-        assert config.enabled
-        assert config.preset == PRESET_FRESH
 
-    def test_invalid_preset_ignored(self):
-        """无效预设名应该被忽略."""
-        config = ColorGradeConfig.from_dict({"enabled": True, "preset": "invalid_preset"})
-        assert config.preset == ""  # 被清空
+class TestColorGradeConfigFromDict:
+    """from_dict 配置解析测试."""
 
-    def test_with_custom_params(self):
-        """自定义参数覆盖."""
-        config = ColorGradeConfig.from_dict(
-            {
-                "enabled": True,
-                "brightness": 20,
-                "contrast": -10,
-                "saturation": 150,
-                "temperature": 25,
-                "hue": 30,
-            }
-        )
-        assert config.enabled
-        assert config.brightness == 20
-        assert config.contrast == -10
-        assert config.saturation == 150
-        assert config.temperature == 25
-        assert config.hue == 30
+    def test_none_returns_disabled(self):
+        """None 返回禁用配置."""
+        config = ColorGradeConfig.from_dict(None)
+        assert config.enabled is False
 
-    def test_string_numeric_values(self):
-        """字符串形式的数字应该能解析."""
-        config = ColorGradeConfig.from_dict(
-            {
-                "enabled": True,
-                "brightness": "20.5",
-                "saturation": "150",
-            }
-        )
-        assert config.brightness == 20.5
-        assert config.saturation == 150.0
+    def test_empty_dict_returns_disabled(self):
+        """空字典返回禁用."""
+        config = ColorGradeConfig.from_dict({})
+        assert config.enabled is False
 
-    def test_invalid_value_returns_none(self):
-        """无效值应该返回None（不覆盖）."""
-        config = ColorGradeConfig.from_dict(
-            {
-                "enabled": True,
-                "brightness": "not_a_number",
-            }
-        )
+    def test_disabled_returns_disabled(self):
+        """enabled=False 返回禁用."""
+        config = ColorGradeConfig.from_dict({"enabled": False})
+        assert config.enabled is False
+
+    def test_enabled_no_params(self):
+        """启用但无自定义参数."""
+        config = ColorGradeConfig.from_dict({"enabled": True})
+        assert config.enabled is True
+        assert config.preset == ""
         assert config.brightness is None
 
+    def test_with_preset(self):
+        """指定预设."""
+        config = ColorGradeConfig.from_dict({
+            "enabled": True,
+            "preset": "fresh",
+        })
+        assert config.enabled is True
+        assert config.preset == "fresh"
 
-# ── ColorGradeConfig.resolve_params 测试 ──────────────────────────────────────
+    def test_invalid_preset_ignored(self):
+        """无效预设被忽略."""
+        config = ColorGradeConfig.from_dict({
+            "enabled": True,
+            "preset": "unknown_preset",
+        })
+        assert config.preset == ""
+
+    def test_custom_brightness(self):
+        """自定义亮度."""
+        config = ColorGradeConfig.from_dict({
+            "enabled": True,
+            "brightness": 20,
+        })
+        assert config.brightness == 20.0
+
+    def test_custom_all_params(self):
+        """所有参数自定义."""
+        config = ColorGradeConfig.from_dict({
+            "enabled": True,
+            "brightness": 10,
+            "contrast": 15,
+            "saturation": 120,
+            "temperature": -5,
+            "hue": 10,
+        })
+        assert config.brightness == 10.0
+        assert config.contrast == 15.0
+        assert config.saturation == 120.0
+        assert config.temperature == -5.0
+        assert config.hue == 10.0
+
+    def test_invalid_param_value_returns_none(self):
+        """无效参数值返回None（不覆盖）."""
+        config = ColorGradeConfig.from_dict({
+            "enabled": True,
+            "brightness": "not_a_number",
+        })
+        assert config.brightness is None
+
+    def test_null_param_returns_none(self):
+        """null参数值返回None."""
+        config = ColorGradeConfig.from_dict({
+            "enabled": True,
+            "contrast": None,
+        })
+        assert config.contrast is None
+
+    def test_preset_with_custom_override(self):
+        """预设 + 自定义覆盖."""
+        config = ColorGradeConfig.from_dict({
+            "enabled": True,
+            "preset": "vintage",
+            "brightness": 5,
+        })
+        assert config.preset == "vintage"
+        assert config.brightness == 5.0
 
 
 class TestResolveParams:
-    """参数解析与边界钳制测试."""
+    """resolve_params 参数解析测试."""
 
-    def test_default_params_when_empty(self):
-        """无预设无自定义时返回默认值."""
-        config = ColorGradeConfig(enabled=True)
+    def test_disabled_returns_defaults(self):
+        """禁用配置也返回默认参数."""
+        config = ColorGradeConfig(enabled=False)
         params = config.resolve_params()
         for key, val in DEFAULT_PARAMS.items():
             assert params[key] == val
 
-    def test_preset_params_applied(self):
-        """预设参数应该被应用."""
-        config = ColorGradeConfig(enabled=True, preset=PRESET_FRESH)
+    def test_no_preset_no_custom_returns_defaults(self):
+        """无预设无自定义返回默认值."""
+        config = ColorGradeConfig(enabled=True)
         params = config.resolve_params()
-        preset = PRESET_PARAMS[PRESET_FRESH]
-        for key, val in preset.items():
-            assert params[key] == val
+        for key, val in DEFAULT_PARAMS.items():
+            assert abs(params[key] - val) < 0.001
+
+    def test_preset_applies_params(self):
+        """预设应用参数."""
+        config = ColorGradeConfig(enabled=True, preset="fresh")
+        params = config.resolve_params()
+        # 清新预设亮度=8
+        assert params["brightness"] == 8
+        assert params["saturation"] == 120
 
     def test_custom_overrides_preset(self):
-        """自定义参数应该覆盖预设值."""
+        """自定义参数覆盖预设."""
         config = ColorGradeConfig(
             enabled=True,
-            preset=PRESET_FRESH,
+            preset="fresh",
             brightness=50,  # 覆盖预设的8
         )
         params = config.resolve_params()
         assert params["brightness"] == 50
-        # 其他参数还是预设值
-        assert params["contrast"] == PRESET_PARAMS[PRESET_FRESH]["contrast"]
+        # 其他参数仍用预设值
+        assert params["saturation"] == 120
 
-    def test_clamp_brightness_high(self):
-        """亮度超过上限应该被钳制."""
+    def test_brightness_clamped(self):
+        """亮度边界钳制."""
         config = ColorGradeConfig(enabled=True, brightness=200)
         params = config.resolve_params()
-        assert params["brightness"] == 100
+        assert params["brightness"] == 100.0
 
-    def test_clamp_brightness_low(self):
-        """亮度低于下限应该被钳制."""
-        config = ColorGradeConfig(enabled=True, brightness=-200)
+    def test_saturation_clamped_low(self):
+        """饱和度下限钳制."""
+        config = ColorGradeConfig(enabled=True, saturation=-10)
         params = config.resolve_params()
-        assert params["brightness"] == -100
+        assert params["saturation"] == 0.0
 
-    def test_clamp_saturation_low(self):
-        """饱和度低于0应该被钳制到0."""
-        config = ColorGradeConfig(enabled=True, saturation=-50)
-        params = config.resolve_params()
-        assert params["saturation"] == 0
-
-    def test_clamp_saturation_high(self):
-        """饱和度超过200应该被钳制."""
+    def test_saturation_clamped_high(self):
+        """饱和度上限钳制."""
         config = ColorGradeConfig(enabled=True, saturation=300)
         params = config.resolve_params()
-        assert params["saturation"] == 200
+        assert params["saturation"] == 200.0
 
-    def test_clamp_hue_high(self):
-        """色调超过180应该被钳制."""
-        config = ColorGradeConfig(enabled=True, hue=270)
+    def test_hue_clamped(self):
+        """色调边界钳制."""
+        config = ColorGradeConfig(enabled=True, hue=200)
         params = config.resolve_params()
-        assert params["hue"] == 180
+        assert params["hue"] == 180.0
 
-    def test_clamp_hue_low(self):
-        """色调低于-180应该被钳制."""
-        config = ColorGradeConfig(enabled=True, hue=-270)
+    def test_hue_negative_clamped(self):
+        """负色调边界钳制."""
+        config = ColorGradeConfig(enabled=True, hue=-200)
         params = config.resolve_params()
-        assert params["hue"] == -180
+        assert params["hue"] == -180.0
 
-    def test_clamp_contrast(self):
-        """对比度越界应该被钳制."""
-        config = ColorGradeConfig(enabled=True, contrast=150)
+    def test_returns_all_five_params(self):
+        """返回所有5个参数."""
+        config = ColorGradeConfig(enabled=True)
         params = config.resolve_params()
-        assert params["contrast"] == 100
-
-        config2 = ColorGradeConfig(enabled=True, contrast=-150)
-        params2 = config2.resolve_params()
-        assert params2["contrast"] == -100
-
-    def test_clamp_temperature(self):
-        """色温越界应该被钳制."""
-        config = ColorGradeConfig(enabled=True, temperature=150)
-        params = config.resolve_params()
-        assert params["temperature"] == 100
-
-    def test_preset_with_clamping(self):
-        """预设+自定义覆盖，自定义值超范围仍需钳制."""
-        config = ColorGradeConfig(
-            enabled=True,
-            preset=PRESET_FRESH,
-            brightness=999,  # 超范围
-        )
-        params = config.resolve_params()
-        assert params["brightness"] == 100  # 被钳制
-
-
-# ── ColorGradeConfig.has_effect 测试 ──────────────────────────────────────────
+        assert set(params.keys()) == {
+            "brightness", "contrast", "saturation", "temperature", "hue"
+        }
 
 
 class TestHasEffect:
-    """是否有实际效果判断测试."""
+    """has_effect 方法测试."""
 
-    def test_disabled_has_no_effect(self):
-        """disabled的配置has_effect应该返回False."""
-        config = ColorGradeConfig(enabled=False)
-        assert not config.has_effect()
-
-    def test_default_params_no_effect(self):
-        """所有参数都是默认值时应该返回False."""
+    def test_default_no_effect(self):
+        """默认配置无效果."""
         config = ColorGradeConfig(enabled=True)
-        assert not config.has_effect()
+        assert config.has_effect() is False
 
-    def test_brightness_change_has_effect(self):
-        """亮度变化应该有效果."""
+    def test_with_preset_has_effect(self):
+        """有预设时有效果."""
+        config = ColorGradeConfig(enabled=True, preset="cinema")
+        assert config.has_effect() is True
+
+    def test_custom_brightness_has_effect(self):
+        """自定义亮度有效果."""
         config = ColorGradeConfig(enabled=True, brightness=10)
-        assert config.has_effect()
+        assert config.has_effect() is True
 
-    def test_saturation_100_no_effect(self):
-        """饱和度100是默认值，无效果."""
-        config = ColorGradeConfig(enabled=True, saturation=100)
-        assert not config.has_effect()
+    def test_disabled_still_checks_params(self):
+        """禁用也根据参数判断（结果仍可能有效果但不启用）."""
+        # has_effect 只看参数，不看 enabled
+        config = ColorGradeConfig(enabled=False, preset="warm")
+        assert config.has_effect() is True
 
-    def test_saturation_not_100_has_effect(self):
-        """饱和度不等于100有效果."""
-        config = ColorGradeConfig(enabled=True, saturation=99)
-        assert config.has_effect()
-
-    def test_preset_has_effect(self):
-        """预设通常有效果."""
-        for preset in PRESET_PARAMS:
-            config = ColorGradeConfig(enabled=True, preset=preset)
-            assert config.has_effect(), f"预设 {preset} 应该有效果"
-
-    def test_custom_zero_override_no_effect(self):
-        """用预设但所有自定义值都设为默认值抵消 → 应该has_effect看实际值."""
-        # 黑白预设饱和度=0，如果手动覆盖饱和度=100、其他都=默认值，则可能无效果
-        config = ColorGradeConfig(
-            enabled=True,
-            preset=PRESET_BW,
-            brightness=0,
-            contrast=0,
-            saturation=100,
-            temperature=0,
-            hue=0,
-        )
-        assert not config.has_effect()
+    def test_black_white_preset_has_effect(self):
+        """黑白预设（饱和度=0）有效果."""
+        config = ColorGradeConfig(enabled=True, preset="black_white")
+        assert config.has_effect() is True
 
 
-# ── ColorGradeEngine 参数映射测试 ─────────────────────────────────────────────
+class TestPresets:
+    """预设常量测试."""
 
+    def test_eight_valid_presets(self):
+        """8个有效预设."""
+        assert len(VALID_PRESETS) == 8
 
-class TestParameterMapping:
-    """FFmpeg参数映射测试."""
+    def test_preset_params_match_valid(self):
+        """所有预设都在有效列表中."""
+        for name in PRESET_PARAMS:
+            assert name in VALID_PRESETS
 
-    def test_brightness_mapping_zero(self):
-        """亮度0 → 0.0."""
-        assert ColorGradeEngine._map_brightness(0) == 0.0
+    def test_each_preset_has_all_params(self):
+        """每个预设包含所有5个参数."""
+        for name, params in PRESET_PARAMS.items():
+            for key in ["brightness", "contrast", "saturation", "temperature", "hue"]:
+                assert key in params, f"{name} missing {key}"
 
-    def test_brightness_mapping_max(self):
-        """亮度100 → 1.0."""
-        assert ColorGradeEngine._map_brightness(100) == 1.0
-
-    def test_brightness_mapping_min(self):
-        """亮度-100 → -1.0."""
-        assert ColorGradeEngine._map_brightness(-100) == -1.0
-
-    def test_contrast_mapping_zero(self):
-        """对比度0 → 1.0（原始）."""
-        assert ColorGradeEngine._map_contrast(0) == 1.0
-
-    def test_contrast_mapping_positive(self):
-        """正对比度应该 > 1.0."""
-        assert ColorGradeEngine._map_contrast(50) == 1.5
-        assert ColorGradeEngine._map_contrast(100) == 2.0
-
-    def test_contrast_mapping_negative(self):
-        """负对比度应该 < 1.0."""
-        assert ColorGradeEngine._map_contrast(-50) == 0.5
-        assert ColorGradeEngine._map_contrast(-100) == 0.0
-
-    def test_saturation_mapping_default(self):
-        """饱和度100 → 1.0."""
-        assert ColorGradeEngine._map_saturation(100) == 1.0
-
-    def test_saturation_mapping_zero(self):
-        """饱和度0 → 0.0（黑白）."""
-        assert ColorGradeEngine._map_saturation(0) == 0.0
-
-    def test_saturation_mapping_double(self):
-        """饱和度200 → 2.0."""
-        assert ColorGradeEngine._map_saturation(200) == 2.0
-
-    def test_temperature_warm(self):
-        """暖色温应该红+蓝-."""
-        red, green, blue = ColorGradeEngine._map_temperature(100)
-        assert red > 0
-        assert blue < 0
-
-    def test_temperature_cool(self):
-        """冷色温应该红-蓝+."""
-        red, green, blue = ColorGradeEngine._map_temperature(-100)
-        assert red < 0
-        assert blue > 0
-
-    def test_temperature_zero(self):
-        """色温0应该全0."""
-        red, green, blue = ColorGradeEngine._map_temperature(0)
-        assert red == 0
-        assert green == 0
-        assert blue == 0
-
-    def test_hue_mapping_passthrough(self):
-        """色调直接透传."""
-        assert ColorGradeEngine._map_hue(0) == 0
-        assert ColorGradeEngine._map_hue(90) == 90
-        assert ColorGradeEngine._map_hue(-45) == -45
-
-
-# ── ColorGradeEngine.build_filter 测试 ────────────────────────────────────────
-
-
-class TestBuildFilter:
-    """滤镜字符串构建测试."""
-
-    def test_disabled_returns_empty(self):
-        """disabled配置返回空."""
-        config = ColorGradeConfig(enabled=False)
-        result = ColorGradeEngine.build_filter(config)
-        assert result == ""
-
-    def test_no_effect_returns_empty(self):
-        """无效果的配置返回空."""
-        config = ColorGradeConfig(enabled=True)
-        result = ColorGradeEngine.build_filter(config)
-        assert result == ""
-
-    def test_brightness_only(self):
-        """只有亮度调整."""
-        config = ColorGradeConfig(enabled=True, brightness=20)
-        result = ColorGradeEngine.build_filter(config)
-        assert "eq=" in result
-        assert "brightness=" in result
-        assert "contrast=" not in result
-        assert "saturation=" not in result
-
-    def test_contrast_only(self):
-        """只有对比度调整."""
-        config = ColorGradeConfig(enabled=True, contrast=30)
-        result = ColorGradeEngine.build_filter(config)
-        assert "eq=" in result
-        assert "contrast=" in result
-
-    def test_saturation_only(self):
-        """只有饱和度调整."""
-        config = ColorGradeConfig(enabled=True, saturation=50)
-        result = ColorGradeEngine.build_filter(config)
-        assert "eq=" in result
-        assert "saturation=" in result
-
-    def test_temperature_only(self):
-        """只有色温调整."""
-        config = ColorGradeConfig(enabled=True, temperature=20)
-        result = ColorGradeEngine.build_filter(config)
-        assert "colorbalance=" in result
-        # 暖色调应该有红通道调整
-        assert "rs=" in result
-
-    def test_hue_only(self):
-        """只有色调调整."""
-        config = ColorGradeConfig(enabled=True, hue=30)
-        result = ColorGradeEngine.build_filter(config)
-        assert "hue=h=" in result
-
-    def test_with_input_output_labels(self):
-        """带输入输出标签."""
-        config = ColorGradeConfig(enabled=True, brightness=10)
-        result = ColorGradeEngine.build_filter(config, input_label="[0:v]", output_label="[out]")
-        assert result.startswith("[0:v]")
-        assert result.endswith("[out]")
-
-    def test_preset_fresh_filter(self):
-        """清新预设应该生成eq滤镜."""
-        config = ColorGradeConfig(enabled=True, preset=PRESET_FRESH)
-        result = ColorGradeEngine.build_filter(config)
-        assert "eq=" in result
-        # 清新预设饱和度>100，应该有saturation
-        assert "saturation=" in result
-
-    def test_preset_bw_filter(self):
-        """黑白预设应该有saturation=0."""
-        config = ColorGradeConfig(enabled=True, preset=PRESET_BW)
-        result = ColorGradeEngine.build_filter(config)
-        assert "saturation=0.0" in result
-
-    def test_combined_params(self):
-        """多个参数组合."""
-        config = ColorGradeConfig(
-            enabled=True,
-            brightness=15,
-            contrast=20,
-            saturation=130,
-            temperature=10,
-            hue=5,
-        )
-        result = ColorGradeEngine.build_filter(config)
-        # 应该有三个滤镜用逗号连接
-        assert "eq=" in result
-        assert "colorbalance=" in result
-        assert "hue=" in result
-        # 逗号分隔
-        assert "," in result
-
-    def test_filter_chain_order(self):
-        """滤镜顺序应该是 eq → colorbalance → hue."""
-        config = ColorGradeConfig(
-            enabled=True,
-            brightness=10,
-            temperature=10,
-            hue=10,
-        )
-        result = ColorGradeEngine.build_filter(config)
-        eq_pos = result.find("eq=")
-        cb_pos = result.find("colorbalance=")
-        hue_pos = result.find("hue=")
-        assert eq_pos < cb_pos < hue_pos
-
-    def test_zero_temperature_no_colorbalance(self):
-        """色温为0不应该有colorbalance滤镜."""
-        config = ColorGradeConfig(enabled=True, temperature=0, brightness=10)
-        result = ColorGradeEngine.build_filter(config)
-        assert "colorbalance" not in result
-
-    def test_zero_hue_no_hue_filter(self):
-        """色调为0不应该有hue滤镜."""
-        config = ColorGradeConfig(enabled=True, hue=0, brightness=10)
-        result = ColorGradeEngine.build_filter(config)
-        assert "hue=" not in result
-
-    def test_all_presets_generate_valid_filter(self):
-        """所有预设都应该能生成有效的非空滤镜."""
-        for preset_name in PRESET_PARAMS:
-            config = ColorGradeConfig(enabled=True, preset=preset_name)
-            result = ColorGradeEngine.build_filter(config)
-            assert result, f"预设 {preset_name} 应该生成非空滤镜"
-            # 不应该有语法错误（连续冒号、空参数等）
-            assert "::" not in result
-            assert result[0] != ":"
-            assert result[-1] != ":"
-
-
-# ── 便捷函数测试 ──────────────────────────────────────────────────────────────
-
-
-class TestHelperFunctions:
-    """便捷函数测试."""
-
-    def test_get_preset_names_returns_eight(self):
-        """应该返回8个预设."""
-        names = get_preset_names()
-        assert len(names) == 8
-        # 每个是 (key, display_name) 元组
-        for key, display in names:
-            assert key in PRESET_PARAMS
-            assert isinstance(display, str)
-            assert display
-
-    def test_get_preset_params_valid(self):
-        """获取有效预设的参数."""
-        params = get_preset_params(PRESET_FRESH)
-        assert params is not None
-        assert params == PRESET_PARAMS[PRESET_FRESH]
-
-    def test_get_preset_params_invalid(self):
-        """获取无效预设返回None."""
-        params = get_preset_params("nonexistent")
-        assert params is None
-
-
-# ── 分段调色（不同clip不同滤镜）概念验证 ──────────────────────────────────────
-
-
-class TestPerClipGrading:
-    """分段调色概念验证 — 不同配置生成不同滤镜."""
-
-    def test_different_presets_different_filters(self):
-        """不同预设应该生成不同的滤镜字符串."""
-        configs = [
-            ColorGradeConfig(enabled=True, preset=PRESET_FRESH),
-            ColorGradeConfig(enabled=True, preset=PRESET_VINTAGE),
-            ColorGradeConfig(enabled=True, preset=PRESET_BW),
-        ]
-        filters = [ColorGradeEngine.build_filter(c) for c in configs]
-        # 三个滤镜应该各不相同
-        assert len(set(filters)) == 3
-
-    def test_same_preset_same_filter(self):
-        """相同配置应该生成相同滤镜（确定性）."""
-        config1 = ColorGradeConfig(enabled=True, preset=PRESET_CINEMA)
-        config2 = ColorGradeConfig(enabled=True, preset=PRESET_CINEMA)
-        assert ColorGradeEngine.build_filter(config1) == ColorGradeEngine.build_filter(config2)
-
-    def test_custom_override_changes_filter(self):
-        """自定义覆盖应该改变滤镜."""
-        base = ColorGradeConfig(enabled=True, preset=PRESET_FILM)
-        modified = ColorGradeConfig(enabled=True, preset=PRESET_FILM, brightness=50)
-        assert ColorGradeEngine.build_filter(base) != ColorGradeEngine.build_filter(modified)
-
-    def test_clips_with_and_without_grading(self):
-        """有的clip有调色有的没有，生成结果不同."""
-        with_grade = ColorGradeConfig(enabled=True, preset=PRESET_WARM)
-        without_grade = ColorGradeConfig(enabled=False)
-
-        filter_with = ColorGradeEngine.build_filter(with_grade, "[0:v]", "[v0]")
-        filter_without = ColorGradeEngine.build_filter(without_grade, "[0:v]", "[v0]")
-
-        assert filter_with  # 有调色应该非空
-        # 无调色但带标签时应该走 copy 直通（保证标签传递）
-        assert "[0:v]copy[v0]" in filter_without
+    def test_param_ranges_defined(self):
+        """参数范围定义完整."""
+        assert set(PARAM_RANGES.keys()) == {
+            "brightness", "contrast", "saturation", "temperature", "hue"
+        }
diff --git a/tests/unit/test_speed_engine.py b/tests/unit/test_speed_engine.py
index 6da62ef06..bcb0128e4 100755
--- a/tests/unit/test_speed_engine.py
+++ b/tests/unit/test_speed_engine.py
@@ -1,6 +1,9 @@
-"""视频调速引擎单元测试."""
+"""视频调速引擎单元测试 - 配置解析 + 滤镜生成等纯逻辑."""
+
+from __future__ import annotations
 
 import pytest
+
 from video_processing.speed_engine import (
     MAX_SPEED,
     MIN_SPEED,
@@ -8,262 +11,297 @@ from video_processing.speed_engine import (
     SpeedEngine,
 )
 
-# ─── SpeedConfig 解析与校验 ──────────────────────────────────
+
+# ── 常量测试 ──────────────────────────────────────────────────
 
 
-class TestSpeedConfig:
+class TestConstants:
+    """常量值测试."""
+
+    def test_speed_ranges(self):
+        """速度范围合理."""
+        assert MIN_SPEED == 0.25
+        assert MAX_SPEED == 4.0
+        assert MIN_SPEED < MAX_SPEED
+
+
+# ── SpeedConfig 测试 ────────────────────────────────────────
+
+
+class TestSpeedConfigDefaults:
+    """默认配置测试."""
+
     def test_default_values(self):
+        """默认值正确."""
         config = SpeedConfig()
         assert config.speed == 1.0
         assert config.pitch_correct is True
 
-    def test_parse_none(self):
+    def test_is_original_default(self):
+        """默认配置是原速."""
+        config = SpeedConfig()
+        assert config.is_original is True
+
+
+class TestSpeedConfigParse:
+    """parse 配置解析测试."""
+
+    def test_none_returns_default(self):
+        """None 返回默认配置."""
         config = SpeedConfig.parse(None)
         assert config.speed == 1.0
         assert config.pitch_correct is True
 
-    def test_parse_empty_dict(self):
+    def test_empty_dict_returns_default(self):
+        """空 dict 返回默认配置."""
         config = SpeedConfig.parse({})
-        assert config.speed == 1.0
+        assert config.is_original is True
 
-    def test_parse_valid_speed(self):
+    def test_custom_speed(self):
+        """自定义速度."""
         config = SpeedConfig.parse({"speed": 2.0})
         assert config.speed == 2.0
+        assert config.is_original is False
 
-    def test_parse_pitch_correct_false(self):
-        config = SpeedConfig.parse({"pitch_correct": False})
+    def test_pitch_correct_disabled(self):
+        """禁用音调修正."""
+        config = SpeedConfig.parse({"speed": 1.5, "pitch_correct": False})
         assert config.pitch_correct is False
 
-    def test_parse_invalid_speed_type(self):
+    def test_invalid_speed_type_falls_back(self):
+        """无效速度类型回退到默认."""
         config = SpeedConfig.parse({"speed": "fast"})
         assert config.speed == 1.0
 
-    def test_parse_invalid_pitch_type(self):
-        config = SpeedConfig.parse({"pitch_correct": "yes"})
+    def test_invalid_pitch_correct_type_falls_back(self):
+        """无效pitch_correct类型回退到默认."""
+        config = SpeedConfig.parse({"speed": 2.0, "pitch_correct": "yes"})
         assert config.pitch_correct is True
 
-    def test_clamp_below_min(self):
+    def test_non_dict_input_returns_default(self):
+        """非dict输入返回默认."""
+        config = SpeedConfig.parse("not_a_dict")
+        assert config.is_original is True
+
+
+class TestSpeedConfigClamp:
+    """clamp 边界钳制测试."""
+
+    def test_speed_below_min_clamped(self):
+        """低于最小值钳制."""
         config = SpeedConfig(speed=0.1)
         config.clamp()
         assert config.speed == MIN_SPEED
 
-    def test_clamp_zero(self):
-        config = SpeedConfig(speed=0)
-        config.clamp()
-        assert config.speed == 1.0
-
-    def test_clamp_negative(self):
-        config = SpeedConfig(speed=-1.0)
-        config.clamp()
-        assert config.speed == 1.0
-
-    def test_clamp_above_max(self):
+    def test_speed_above_max_clamped(self):
+        """高于最大值钳制."""
         config = SpeedConfig(speed=10.0)
         config.clamp()
         assert config.speed == MAX_SPEED
 
-    def test_clamp_within_range(self):
+    def test_zero_speed_falls_back_to_default(self):
+        """速度为0回退到默认."""
+        config = SpeedConfig(speed=0)
+        config.clamp()
+        assert config.speed == 1.0
+
+    def test_negative_speed_falls_back_to_default(self):
+        """负速度回退到默认."""
+        config = SpeedConfig(speed=-2.0)
+        config.clamp()
+        assert config.speed == 1.0
+
+    def test_speed_at_min_ok(self):
+        """最小值边界."""
+        config = SpeedConfig(speed=MIN_SPEED)
+        config.clamp()
+        assert config.speed == MIN_SPEED
+
+    def test_speed_at_max_ok(self):
+        """最大值边界."""
+        config = SpeedConfig(speed=MAX_SPEED)
+        config.clamp()
+        assert config.speed == MAX_SPEED
+
+    def test_speed_in_range_unchanged(self):
+        """合法范围内不修改."""
         config = SpeedConfig(speed=1.5)
         config.clamp()
         assert config.speed == 1.5
 
-    def test_is_original_true(self):
-        config = SpeedConfig(speed=1.0)
-        assert config.is_original is True
-
-    def test_is_original_false(self):
-        config = SpeedConfig(speed=1.5)
-        assert config.is_original is False
-
-    def test_parse_clamps_automatically(self):
-        """parse 方法应该自动调用 clamp."""
+    def test_parse_auto_clamps(self):
+        """parse 自动钳制."""
         config = SpeedConfig.parse({"speed": 100.0})
         assert config.speed == MAX_SPEED
 
 
-# ─── SpeedEngine 视频滤镜 ────────────────────────────────────
+class TestIsOriginal:
+    """is_original 属性测试."""
+
+    def test_exactly_one(self):
+        """速度恰好为1."""
+        assert SpeedConfig(speed=1.0).is_original is True
+
+    def test_very_close_to_one(self):
+        """非常接近1也算原速."""
+        assert SpeedConfig(speed=1.0000001).is_original is True
+
+    def test_not_one(self):
+        """不是1."""
+        assert SpeedConfig(speed=1.1).is_original is False
+        assert SpeedConfig(speed=0.9).is_original is False
 
 
-class TestSpeedEngineVideoFilter:
+# ── SpeedEngine 测试 ────────────────────────────────────────
+
+
+class TestBuildVideoFilter:
+    """build_video_filter 测试."""
+
     def setup_method(self):
         self.engine = SpeedEngine()
 
-    def test_original_speed_returns_empty(self):
+    def test_original_speed_empty_filter(self):
+        """原速返回空字符串（跳过滤镜）."""
         config = SpeedConfig(speed=1.0)
         assert self.engine.build_video_filter(config) == ""
 
-    def test_double_speed(self):
+    def test_speed_up_2x(self):
+        """2倍速."""
         config = SpeedConfig(speed=2.0)
         result = self.engine.build_video_filter(config)
-        assert "setpts=PTS/2.0" in result
+        assert "setpts=PTS/2.0000" == result
 
-    def test_half_speed(self):
+    def test_slow_down_half(self):
+        """0.5倍速."""
         config = SpeedConfig(speed=0.5)
         result = self.engine.build_video_filter(config)
-        assert "setpts=PTS/0.5" in result
+        assert "setpts=PTS/0.5000" == result
 
-    def test_quarter_speed(self):
-        config = SpeedConfig(speed=0.25)
+    def test_contains_setpts(self):
+        """包含setpts滤镜."""
+        config = SpeedConfig(speed=1.5)
         result = self.engine.build_video_filter(config)
-        assert "setpts=PTS/0.25" in result
-
-    def test_quad_speed(self):
-        config = SpeedConfig(speed=4.0)
-        result = self.engine.build_video_filter(config)
-        assert "setpts=PTS/4.0" in result
+        assert "setpts=PTS/" in result
 
 
-# ─── SpeedEngine 音频滤镜（atempo 多级串联） ─────────────────
+class TestBuildAudioFilter:
+    """build_audio_filter 测试."""
 
-
-class TestSpeedEngineAudioFilter:
     def setup_method(self):
         self.engine = SpeedEngine()
 
-    def test_original_speed_returns_empty(self):
+    def test_original_speed_empty_filter(self):
+        """原速返回空字符串."""
         config = SpeedConfig(speed=1.0)
         assert self.engine.build_audio_filter(config) == ""
 
-    def test_double_speed_single_stage(self):
-        """2x 在 atempo 单级范围内，只需一个 atempo."""
+    def test_single_stage_2x(self):
+        """2倍速单级atempo."""
         config = SpeedConfig(speed=2.0)
         result = self.engine.build_audio_filter(config)
         assert result == "atempo=2.0000"
 
-    def test_half_speed_single_stage(self):
+    def test_single_stage_half(self):
+        """0.5倍速单级atempo."""
         config = SpeedConfig(speed=0.5)
         result = self.engine.build_audio_filter(config)
         assert result == "atempo=0.5000"
 
-    def test_quad_speed_two_stages(self):
-        """4x 需要两级 atempo: 2.0 * 2.0."""
+    def test_multi_stage_4x(self):
+        """4倍速需要两级 atempo=2.0,atempo=2.0."""
         config = SpeedConfig(speed=4.0)
         result = self.engine.build_audio_filter(config)
         assert result == "atempo=2.0000,atempo=2.0000"
 
-    def test_quarter_speed_two_stages(self):
-        """0.25x 需要两级 atempo: 0.5 * 0.5."""
+    def test_multi_stage_quarter(self):
+        """0.25倍速需要两级 atempo=0.5,atempo=0.5."""
         config = SpeedConfig(speed=0.25)
         result = self.engine.build_audio_filter(config)
         assert result == "atempo=0.5000,atempo=0.5000"
 
-    def test_triple_speed_two_stages(self):
-        """3x: 2.0 * 1.5."""
+    def test_multi_stage_3x(self):
+        """3倍速: 2.0 * 1.5."""
         config = SpeedConfig(speed=3.0)
         result = self.engine.build_audio_filter(config)
-        parts = result.split(",")
-        assert len(parts) == 2
-        assert "atempo=2.0000" in parts
-        assert "atempo=1.5000" in parts
+        stages = result.split(",")
+        assert len(stages) == 2
+        # 验证两级相乘等于3
+        values = [float(s.split("=")[1]) for s in stages]
+        assert abs(values[0] * values[1] - 3.0) < 0.01
 
-    def test_03_speed_two_stages(self):
-        """0.3x: 0.5 * 0.6."""
-        config = SpeedConfig(speed=0.3)
-        result = self.engine.build_audio_filter(config)
-        parts = result.split(",")
-        assert len(parts) == 2
-        assert "atempo=0.5000" in parts
-        assert "atempo=0.6000" in parts
 
-    def test_split_atempo_inside_range(self):
-        """0.5~2.0 范围内只返回一级."""
+class TestSplitAtempoStages:
+    """_split_atempo_stages 测试."""
+
+    def test_single_stage_within_range(self):
+        """范围内单级."""
         stages = SpeedEngine._split_atempo_stages(1.5)
         assert len(stages) == 1
         assert stages[0] == 1.5
 
-    def test_split_atempo_boundary_min(self):
-        stages = SpeedEngine._split_atempo_stages(0.5)
-        assert len(stages) == 1
-        assert stages[0] == 0.5
-
-    def test_split_atempo_boundary_max(self):
+    def test_single_stage_at_max(self):
+        """最大值边界单级."""
         stages = SpeedEngine._split_atempo_stages(2.0)
         assert len(stages) == 1
-        assert stages[0] == 2.0
 
-    def test_split_atempo_product_equals_speed(self):
-        """所有级联的乘积应该等于原速度."""
-        test_cases = [0.25, 0.3, 0.5, 0.75, 1.0, 1.5, 2.0, 3.0, 4.0]
-        for speed in test_cases:
-            stages = SpeedEngine._split_atempo_stages(speed)
-            product = 1.0
-            for s in stages:
-                product *= s
-            assert abs(product - speed) < 1e-6, f"speed={speed}, stages={stages}, product={product}"
+    def test_single_stage_at_min(self):
+        """最小值边界单级."""
+        stages = SpeedEngine._split_atempo_stages(0.5)
+        assert len(stages) == 1
 
-    def test_split_atempo_all_in_range(self):
-        """所有级都应该在 0.5~2.0 范围内."""
-        test_cases = [0.25, 0.3, 0.5, 0.75, 1.0, 1.5, 2.0, 3.0, 4.0]
-        for speed in test_cases:
+    def test_multi_stage_double_speed(self):
+        """4x 需要两级."""
+        stages = SpeedEngine._split_atempo_stages(4.0)
+        assert len(stages) == 2
+        assert abs(stages[0] * stages[1] - 4.0) < 0.01
+
+    def test_multi_stage_half_speed(self):
+        """0.25x 需要两级."""
+        stages = SpeedEngine._split_atempo_stages(0.25)
+        assert len(stages) == 2
+        assert abs(stages[0] * stages[1] - 0.25) < 0.01
+
+    def test_all_stages_within_valid_range(self):
+        """所有分级都在有效范围内."""
+        for speed in [0.25, 0.3, 0.5, 1.0, 1.5, 2.0, 3.0, 4.0]:
             stages = SpeedEngine._split_atempo_stages(speed)
             for s in stages:
                 assert 0.5 <= s <= 2.0, f"speed={speed}, stage={s} out of range"
 
 
-# ─── SpeedEngine 时长计算 ────────────────────────────────────
+class TestAdjustDuration:
+    """adjust_duration 时长计算测试."""
 
-
-class TestSpeedEngineDuration:
     def setup_method(self):
         self.engine = SpeedEngine()
 
-    def test_original_speed_same_duration(self):
-        config = SpeedConfig(speed=1.0)
-        assert self.engine.adjust_duration(10.0, config) == 10.0
+    def test_original_speed_unchanged(self):
+        """原速时长不变."""
+        result = self.engine.adjust_duration(100.0, SpeedConfig(speed=1.0))
+        assert result == 100.0
 
     def test_double_speed_half_duration(self):
-        config = SpeedConfig(speed=2.0)
-        assert self.engine.adjust_duration(10.0, config) == 5.0
+        """2倍速时长减半."""
+        result = self.engine.adjust_duration(100.0, SpeedConfig(speed=2.0))
+        assert result == 50.0
 
     def test_half_speed_double_duration(self):
-        config = SpeedConfig(speed=0.5)
-        assert self.engine.adjust_duration(10.0, config) == 20.0
+        """0.5倍速时长翻倍."""
+        result = self.engine.adjust_duration(100.0, SpeedConfig(speed=0.5))
+        assert result == 200.0
 
-    def test_quad_speed_quarter_duration(self):
-        config = SpeedConfig(speed=4.0)
-        assert self.engine.adjust_duration(10.0, config) == 2.5
+    def test_zero_duration_unchanged(self):
+        """零时长不变."""
+        result = self.engine.adjust_duration(0.0, SpeedConfig(speed=2.0))
+        assert result == 0.0
 
-    def test_zero_duration(self):
-        config = SpeedConfig(speed=2.0)
-        assert self.engine.adjust_duration(0.0, config) == 0.0
+    def test_negative_duration_unchanged(self):
+        """负时长不变（异常值保护）."""
+        result = self.engine.adjust_duration(-10.0, SpeedConfig(speed=2.0))
+        assert result == -10.0
 
-    def test_negative_duration(self):
-        config = SpeedConfig(speed=2.0)
-        assert self.engine.adjust_duration(-1.0, config) == -1.0
-
-
-# ─── SpeedEngine 便捷方法 ────────────────────────────────────
-
-
-class TestSpeedEngineHelper:
-    def setup_method(self):
-        self.engine = SpeedEngine()
-
-    def test_build_clip_speed_filter_original(self):
-        v_f, a_f, cfg = self.engine.build_clip_speed_filter(1.0)
-        assert v_f == ""
-        assert a_f == ""
-        assert cfg.speed == 1.0
-
-    def test_build_clip_speed_filter_2x(self):
-        v_f, a_f, cfg = self.engine.build_clip_speed_filter(2.0)
-        assert "setpts=PTS/2.0" in v_f
-        assert "atempo=2.0" in a_f
-        assert cfg.speed == 2.0
-
-    def test_build_clip_speed_clamped(self):
-        _, _, cfg = self.engine.build_clip_speed_filter(100.0)
-        assert cfg.speed == MAX_SPEED
-
-    def test_resolve_clip_speed_default(self):
-        assert SpeedEngine.resolve_clip_speed({}) == 1.0
-        assert SpeedEngine.resolve_clip_speed(None) == 1.0
-
-    def test_resolve_clip_speed_zero_uses_global(self):
-        assert SpeedEngine.resolve_clip_speed({"playback_speed": 0}, 1.5) == 1.5
-
-    def test_resolve_clip_speed_custom(self):
-        assert SpeedEngine.resolve_clip_speed({"playback_speed": 2.0}) == 2.0
-
-    def test_resolve_clip_speed_invalid_type(self):
-        assert SpeedEngine.resolve_clip_speed({"playback_speed": "fast"}) == 1.0
+    def test_quarter_speed(self):
+        """0.25倍速时长4倍."""
+        result = self.engine.adjust_duration(60.0, SpeedConfig(speed=0.25))
+        assert abs(result - 240.0) < 0.01