原文：

The testing pyramid is a framework that guides test strategy by proportion. At the base are unit tests — numerous, fast, and isolated, verifying individual components. The middle layer contains integration tests, which check how components interact. At the top are end-to-end tests — few, slow, but validating complete user scenarios. This distribution is pragmatic: unit tests catch most bugs cheaply, while E2E tests ensure critical flows work. Over-relying on E2E tests leads to slow feedback loops and brittle test suites that break on minor UI changes.

翻译：

测试金字塔是一个按比例指导测试策略的框架。底部是单元测试——数量多、速度快、隔离性好，验证单个组件。中间层包含集成测试，检查组件之间如何交互。顶部是端到端测试——数量少、速度慢，但验证完整的用户场景。这种分布是务实的：单元测试以低成本捕获大多数bug，而端到端测试确保关键流程正常工作。过度依赖端到端测试会导致反馈循环缓慢和脆弱的测试套件，在微小的UI变化时就会破坏。

词汇注释：

• pyramid /ˈpɪrəmɪd/：金字塔
• proportion /prəˈpɔːrʃn/：比例
• unit test /ˈjuːnɪt test/：单元测试
• integration test /ˌɪntɪˈɡreɪʃn test/：集成测试
• end-to-end test /end tuː end test/：端到端测试
• pragmatic /præɡˈmætɪk/：务实的
• feedback loop /ˈfiːdbæk luːp/：反馈循环
• brittle /ˈbrɪtl/：脆弱的