Best Practices for Test-Driven Development (TDD)

Best Practices for Test-Driven Development (TDD)

  • As part of the “Best Practices” series by Uplatz

 

Welcome to this discipline-first edition of the Uplatz Best Practices series — where quality is built in, not tested in.
Today’s focus: Test-Driven Development (TDD) — a software development process that leads to better code, faster debugging, and more confident releases.

🧪 What is Test-Driven Development?

Test-Driven Development (TDD) is a development methodology where tests are written before the code that satisfies them.
It follows a simple 3-step cycle:

  1. Red – Write a failing test for a new feature

  2. Green – Write just enough code to make the test pass

  3. Refactor – Clean up the code while keeping the test green

This loop ensures that every line of code is justified by a test.

✅ Best Practices for Test-Driven Development (TDD)

TDD is about thinking before coding — and validating intent with precision. Here’s how to do it right:

1. Write the Smallest Failing Test First

🧪 Keep Your Initial Test Narrow and Focused
Avoid Testing Multiple Behaviors at Once
📏 Use Assert-First Thinking: What Do You Expect the Code to Do?

2. Focus on Behavior, Not Implementation

🎯 Write Tests Based on External Outputs or Effects
📦 Don’t Hardwire Tests to Internal Variables or Functions
🧠 Let Tests Guide Design, Not Dictate Structure

3. Keep Tests Fast and Independent

Avoid External Dependencies (e.g., DB, network)
🔁 Mock or Stub I/O Where Necessary
🏃 Run Tests Frequently Without Waiting

4. Refactor Relentlessly

🧹 Refactor Code After the Test Passes — But Keep Tests Passing
📦 Consolidate Logic, Remove Duplication, Improve Naming
🧠 Refactor Tests Too — They’re First-Class Citizens

5. Use Descriptive Test Names

📘 Name Tests to Express Intent: should_throw_if_password_is_empty()
📎 Helps in Debugging, Code Reviews, and Test Reporting
Follows Readability over Brevity

6. Organize Test Files Strategically

🗂️ Mirror Production Code Structure
📦 Group by Feature or Module (not by test type)
🔍 Easy Discoverability for Developers and CI Systems

7. Use Mocks and Fakes Judiciously

🧪 Mock External Dependencies (email, APIs, queues)
🚫 Don’t Overuse Mocks for Core Logic — That Breaks Refactoring
🧩 Use Test Doubles Only Where Needed

8. Integrate TDD With CI/CD

🔄 Run Tests on Every Commit and Pull Request
📈 Track Coverage and Performance Metrics Automatically
🧪 Fail Builds if Tests Fail — Treat as Production Bugs

9. Educate Teams on TDD Discipline

🎓 Run Internal TDD Dojos or Pairing Sessions
🤝 Pair Juniors With Seniors to Reinforce Patterns
🧱 Start With Greenfield Projects or Isolated Modules

10. Use TDD for Design Feedback

🔄 Let Tests Reveal Design Pain Points (e.g., hard-to-test code)
🧠 Use That Feedback to Restructure Code for Better Modularity
🧱 TDD Is as Much About Design as It Is About Testing

💡 Bonus Tip by Uplatz

TDD isn’t slow — broken code is.
Think tests-first, write better code later. Discipline now, velocity forever.

🔁 Follow Uplatz to get more best practices in upcoming posts:

  • Behavior-Driven Development (BDD)

  • Continuous Testing in Agile

  • Writing Mocks With Test Containers

  • Using TDD With Microservices

  • Refactoring Legacy Code With TDD
    …and more on software quality, test architecture, and agile engineering.