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_validation_flow.py

@@ -0,0 +1,269 @@
+"""
+验证流程集成测试
+
+测试完整的验证流程和验证结果收集
+"""
+
+import pytest
+from pathlib import Path
+from validators.validator import Validator
+from validators.result import ValidationResult
+
+
+class TestValidationFlow:
+    """验证流程测试类"""
+
+    def test_validate_valid_yaml(self, sample_yaml):
+        """测试验证有效的 YAML 文件"""
+        validator = Validator()
+        result = validator.validate(sample_yaml)
+
+        assert isinstance(result, ValidationResult)
+        assert result.valid is True
+        assert len(result.errors) == 0
+
+    def test_validate_with_warnings(self, temp_dir):
+        """测试验证包含警告的 YAML"""
+        yaml_content = """
+metadata:
+  size: 16:9
+
+slides:
+  - elements:
+      - type: text
+        box: [8, 1, 3, 1]  # 右边界超出
+        content: "Test"
+        font:
+          size: 4  # 字体太小
+"""
+        yaml_path = temp_dir / "test.yaml"
+        yaml_path.write_text(yaml_content)
+
+        validator = Validator()
+        result = validator.validate(yaml_path)
+
+        # 应该有警告但 valid 仍为 True（没有错误）
+        assert len(result.warnings) > 0
+
+    def test_validate_with_errors(self, temp_dir):
+        """测试验证包含错误的 YAML"""
+        yaml_content = """
+metadata:
+  size: 16:9
+
+slides:
+  - elements:
+      - type: text
+        box: [1, 1, 8, 1]
+        content: "Test"
+        font:
+          color: "red"  # 无效颜色格式
+"""
+        yaml_path = temp_dir / "test.yaml"
+        yaml_path.write_text(yaml_content)
+
+        validator = Validator()
+        result = validator.validate(yaml_path)
+
+        assert result.valid is False
+        assert len(result.errors) > 0
+
+    def test_validate_nonexistent_file(self, temp_dir):
+        """测试验证不存在的文件"""
+        validator = Validator()
+        nonexistent = temp_dir / "nonexistent.yaml"
+        result = validator.validate(nonexistent)
+
+        assert result.valid is False
+        assert len(result.errors) > 0
+
+    def test_collect_multiple_errors(self, temp_dir):
+        """测试收集多个错误"""
+        yaml_content = """
+metadata:
+  size: 16:9
+
+slides:
+  - elements:
+      - type: text
+        box: [1, 1, 8, 1]
+        content: "Test 1"
+        font:
+          color: "red"
+
+      - type: text
+        box: [2, 2, 8, 1]
+        content: "Test 2"
+        font:
+          color: "blue"
+"""
+        yaml_path = temp_dir / "test.yaml"
+        yaml_path.write_text(yaml_content)
+
+        validator = Validator()
+        result = validator.validate(yaml_path)
+
+        # 应该收集到多个错误
+        assert len(result.errors) >= 2
+
+    def test_error_location_information(self, temp_dir):
+        """测试错误包含位置信息"""
+        yaml_content = """
+metadata:
+  size: 16:9
+
+slides:
+  - elements:
+      - type: text
+        box: [1, 1, 8, 1]
+        content: "Test"
+        font:
+          color: "red"
+"""
+        yaml_path = temp_dir / "test.yaml"
+        yaml_path.write_text(yaml_content)
+
+        validator = Validator()
+        result = validator.validate(yaml_path)
+
+        # 错误应该包含位置信息
+        if result.errors:
+            assert "幻灯片 1" in result.errors[0].location
+
+    def test_validate_with_template(self, temp_dir, sample_template):
+        """测试验证使用模板的 YAML"""
+        yaml_content = f"""
+metadata:
+  size: 16:9
+
+slides:
+  - template: title-slide
+    vars:
+      title: "Test Title"
+"""
+        yaml_path = temp_dir / "test.yaml"
+        yaml_path.write_text(yaml_content)
+
+        validator = Validator()
+        result = validator.validate(yaml_path, template_dir=sample_template)
+
+        assert isinstance(result, ValidationResult)
+        # 有效模板应该验证通过
+        assert len(result.errors) == 0
+
+    def test_validate_with_missing_required_variable(self, temp_dir, sample_template):
+        """测试验证缺少必需变量的模板"""
+        yaml_content = f"""
+metadata:
+  size: 16:9
+
+slides:
+  - template: title-slide
+    vars: {{}}
+"""
+        yaml_path = temp_dir / "test.yaml"
+        yaml_path.write_text(yaml_content)
+
+        validator = Validator()
+        result = validator.validate(yaml_path, template_dir=sample_template)
+
+        # 应该有错误（缺少必需的 title 变量）
+        assert len(result.errors) > 0
+
+    def test_categorize_issues_by_level(self, temp_dir):
+        """测试按级别分类问题"""
+        # 创建包含错误和警告的 YAML
+        yaml_content = """
+metadata:
+  size: 16:9
+
+slides:
+  - elements:
+      - type: text
+        box: [1, 1, 8, 1]
+        content: "Test"
+        font:
+          color: "red"  # 错误
+          size: 4       # 警告
+"""
+        yaml_path = temp_dir / "test.yaml"
+        yaml_path.write_text(yaml_content)
+
+        validator = Validator()
+        result = validator.validate(yaml_path)
+
+        # 应该同时有错误和警告
+        assert len(result.errors) > 0
+        assert len(result.warnings) > 0
+
+    def test_format_validation_result(self, temp_dir):
+        """测试验证结果格式化"""
+        yaml_content = """
+metadata:
+  size: 16:9
+
+slides:
+  - elements:
+      - type: text
+        box: [1, 1, 8, 1]
+        content: "Test"
+        font:
+          color: "red"
+"""
+        yaml_path = temp_dir / "test.yaml"
+        yaml_path.write_text(yaml_content)
+
+        validator = Validator()
+        result = validator.validate(yaml_path)
+
+        # 格式化输出
+        output = result.format_output()
+
+        assert "检查" in output
+        if result.errors:
+            assert "错误" in output
+        if result.warnings:
+            assert "警告" in output
+
+    def test_validate_image_resource(self, temp_dir, sample_image):
+        """测试验证图片资源"""
+        yaml_content = f"""
+metadata:
+  size: 16:9
+
+slides:
+  - elements:
+      - type: image
+        box: [1, 1, 4, 3]
+        src: "{sample_image.name}"
+"""
+        yaml_path = temp_dir / "test.yaml"
+        yaml_path.write_text(yaml_content)
+
+        validator = Validator()
+        result = validator.validate(yaml_path)
+
+        # 图片存在，应该没有错误
+        assert len(result.errors) == 0
+
+    def test_validate_missing_image_resource(self, temp_dir):
+        """测试验证不存在的图片资源"""
+        yaml_content = """
+metadata:
+  size: 16:9
+
+slides:
+  - elements:
+      - type: image
+        box: [1, 1, 4, 3]
+        src: "nonexistent.png"
+"""
+        yaml_path = temp_dir / "test.yaml"
+        yaml_path.write_text(yaml_content)
+
+        validator = Validator()
+        result = validator.validate(yaml_path)
+
+        # 应该有错误（图片不存在）
+        assert len(result.errors) > 0
+        assert any("图片文件不存在" in e.message for e in result.errors)