🔍

Understanding Test-Driven Development Principles

Aug 7, 2024

Lecture on Test-Driven Development (TDD)

Introduction

  • Topic: Test-Driven Development (TDD)
  • Audience interaction: Questions about familiarity with TDD, usage of mocks, etc.
  • Encouragement to engage in conferences and share knowledge.

Personal Background

  • Speaker's background: Developer at Huddle, experience with .NET and TDD since 2004.
  • Initially faced resistance to TDD.

Issues with Current TDD Practices

  • Common problems:
    • Excessive test code compared to production code.
    • Slow development process due to extensive testing.
    • Breaking tests when refactoring.
    • Difficulty maintaining and understanding tests.
  • Growing resistance and alternative methodologies:
    • Techniques like program around key, lean software, and duct-tape programming favor rapid development over extensive testing.

Core Issues in TDD Practice

  • Key misunderstanding: Testing implementation details rather than behaviors.
  • Original TDD ethos: Testing should be driven by requirements, not by adding methods.
  • Focus should be on testing the API (publicly exposed surface area) rather than internal implementation details.
  • Behavior-driven approach: Given-When-Then format.

Red-Green-Refactor Cycle

  • Red: Write a test that fails.
  • Green: Make the test pass quickly, even with suboptimal code.
  • Refactor: Improve the code without changing its behavior.
  • Emphasis on not writing new tests during the refactoring step.
  • Aim to decouple tests from implementation details.

Ports and Adapters Architecture

  • Testing pyramid: Majority of tests should be developer tests, fewer integration tests, and minimal system tests.
  • Ports and Adapters (Hexagonal Architecture): Separate domain logic from technology-specific concerns.
    • Core domain (POJOs/POCOs) with adapters for interacting with external systems like databases and UI.
    • Ports act as entry points for different communication methods.
  • Tests should focus on the ports rather than internal implementation details.

Other Testing Insights

  • Mocks: Use sparingly; they should not be the primary method of isolating classes for unit tests.
  • Acceptance Test-Driven Development (ATDD): Mixed opinions; initially rejected but later reconsidered. Focus on understanding customer requirements and guiding developer tests.
  • Behavior-Driven Development (BDD): Initially aimed to clarify TDD by focusing on behaviors. Has since evolved into a full-scale agile methodology.

Summary

  • Test behaviors, not implementations.
  • Use Red-Green-Refactor cycle effectively.
  • Minimize mocks and focus on public APIs.
  • Adopt suitable architecture for testing, like Ports and Adapters.

Additional Resources

  • Recommended reading: Kent Beck's book on TDD.
  • Further discussions: Dialogues between Kent Beck and DHH mediated by Martin Fowler.

Conclusion

  • Encouragement to apply TDD principles correctly for more effective and maintainable test suites.
  • Openness to further questions and discussions.