test: add comprehensive pytest test suite

Add complete test infrastructure for yaml2pptx project with 245+ tests
covering unit, integration, and end-to-end scenarios.

Test structure:
- Unit tests: elements, template system, validators, loaders, utils
- Integration tests: presentation and rendering flows
- E2E tests: CLI commands (convert, check, preview)

Key features:
- PptxFileValidator for Level 2 PPTX validation (file structure,
  element count, content matching, position tolerance)
- Comprehensive fixtures for test data consistency
- Mock-based testing for external dependencies
- Test images generated with PIL/Pillow
- Boundary case coverage for edge scenarios

Dependencies added:
- pytest, pytest-cov, pytest-mock
- pillow (for test image generation)

Documentation updated:
- README.md: test running instructions
- README_DEV.md: test development guide

Co-authored-by: OpenSpec change: add-comprehensive-tests

tests/integration/test_presentation.py

@@ -0,0 +1,186 @@
+"""
+Presentation 类集成测试
+
+测试 Presentation 类的模板加载和幻灯片渲染功能
+"""
+
+import pytest
+from pathlib import Path
+from core.presentation import Presentation
+
+
+class TestPresentationInit:
+    """Presentation 初始化测试"""
+
+    def test_init_with_yaml(self, sample_yaml):
+        """测试使用 YAML 文件初始化"""
+        pres = Presentation(str(sample_yaml))
+        assert pres.data is not None
+        assert "slides" in pres.data
+
+    def test_init_with_template_dir(self, sample_yaml, sample_template):
+        """测试带模板目录初始化"""
+        pres = Presentation(str(sample_yaml), str(sample_template))
+        assert pres.template_dir == sample_template
+
+
+class TestTemplateCaching:
+    """模板缓存测试"""
+
+    def test_template_is_cached(self, temp_dir, sample_template):
+        """测试模板被缓存"""
+        # 创建使用模板的 YAML
+        yaml_content = f"""
+metadata:
+  size: 16:9
+
+slides:
+  - template: title-slide
+    vars:
+      title: "Test"
+"""
+        yaml_path = temp_dir / "test.yaml"
+        yaml_path.write_text(yaml_content)
+
+        pres = Presentation(str(yaml_path), str(sample_template))
+
+        # 第一次获取模板
+        template1 = pres.get_template("title-slide")
+        # 第二次获取模板
+        template2 = pres.get_template("title-slide")
+
+        # 应该是同一个实例（缓存）
+        assert template1 is template2
+
+
+class TestRenderSlide:
+    """render_slide 方法测试"""
+
+    def test_render_simple_slide(self, sample_yaml):
+        """测试渲染简单幻灯片"""
+        pres = Presentation(str(sample_yaml))
+        slide_data = pres.data["slides"][0]
+        rendered = pres.render_slide(slide_data)
+
+        assert "elements" in rendered
+        assert len(rendered["elements"]) > 0
+
+    def test_render_slide_with_template(self, temp_dir, sample_template):
+        """测试渲染使用模板的幻灯片"""
+        yaml_content = f"""
+metadata:
+  size: 16:9
+
+slides:
+  - template: title-slide
+    vars:
+      title: "Test Title"
+      subtitle: "Test Subtitle"
+"""
+        yaml_path = temp_dir / "test.yaml"
+        yaml_path.write_text(yaml_content)
+
+        pres = Presentation(str(yaml_path), str(sample_template))
+        slide_data = pres.data["slides"][0]
+        rendered = pres.render_slide(slide_data)
+
+        # 模板变量应该被替换
+        elements = rendered["elements"]
+        title_elem = next(e for e in elements if e.get("type") == "text" and "Test Title" in e.get("content", ""))
+        assert title_elem is not None
+
+    def test_render_slide_with_conditional_element(self, temp_dir, sample_template):
+        """测试条件渲染元素"""
+        # 有 subtitle 的情况
+        yaml_with = f"""
+metadata:
+  size: 16:9
+
+slides:
+  - template: title-slide
+    vars:
+      title: "Test"
+      subtitle: "With Subtitle"
+"""
+        yaml_path_with = temp_dir / "test_with.yaml"
+        yaml_path_with.write_text(yaml_with)
+
+        pres_with = Presentation(str(yaml_path_with), str(sample_template))
+        slide_data = pres_with.data["slides"][0]
+        rendered_with = pres_with.render_slide(slide_data)
+
+        # 应该有 2 个元素（title 和 subtitle 都显示）
+        assert len(rendered_with["elements"]) == 2
+
+        # 没有 subtitle 的情况
+        yaml_without = f"""
+metadata:
+  size: 16:9
+
+slides:
+  - template: title-slide
+    vars:
+      title: "Test"
+"""
+        yaml_path_without = temp_dir / "test_without.yaml"
+        yaml_path_without.write_text(yaml_without)
+
+        pres_without = Presentation(str(yaml_path_without), str(sample_template))
+        slide_data = pres_without.data["slides"][0]
+        rendered_without = pres_without.render_slide(slide_data)
+
+        # 应该只有 1 个元素（subtitle 不显示）
+        assert len(rendered_without["elements"]) == 1
+
+    def test_render_slide_with_variables(self, temp_dir, sample_template):
+        """测试变量传递"""
+        yaml_content = f"""
+metadata:
+  size: 16:9
+
+slides:
+  - template: title-slide
+    vars:
+      title: "My Title"
+      subtitle: "My Subtitle"
+"""
+        yaml_path = temp_dir / "test.yaml"
+        yaml_path.write_text(yaml_content)
+
+        pres = Presentation(str(yaml_path), str(sample_template))
+        slide_data = pres.data["slides"][0]
+        rendered = pres.render_slide(slide_data)
+
+        # 检查变量是否被正确替换
+        elements = rendered["elements"]
+        assert any("My Title" in e.get("content", "") for e in elements)
+        assert any("My Subtitle" in e.get("content", "") for e in elements)
+
+
+class TestPresentationWithoutTemplate:
+    """无模板的演示文稿测试"""
+
+    def test_render_direct_elements(self, temp_dir):
+        """测试直接渲染元素（不使用模板）"""
+        yaml_content = """
+metadata:
+  size: 16:9
+
+slides:
+  - elements:
+      - type: text
+        box: [1, 1, 8, 1]
+        content: "Direct Text"
+        font:
+          size: 24
+"""
+        yaml_path = temp_dir / "test.yaml"
+        yaml_path.write_text(yaml_content)
+
+        pres = Presentation(str(yaml_path))
+        slide_data = pres.data["slides"][0]
+        rendered = pres.render_slide(slide_data)
+
+        # 元素应该直接被渲染
+        assert len(rendered["elements"]) == 1
+        assert rendered["elements"][0]["content"] == "Direct Text"