The Complete Guide to Starting TDD

Step by step guide to get started with Test-Driven Development

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Motivation

People often ask me how to get started with Test-Driven Development (TDD). There's plenty of information online, but much of it is misleading, making it hard for beginners to learn.

That's why I decided to create the ultimate guide I wish I had when I started learning TDD nearly a decade ago.

You always wanted to learn TDD and don't know where to start? Then let me break it down for you:

1. Learn the TDD cycle

The TDD cycle is the fundamental of TDD. It consists of three phases:

1. Red - Write a failing test: Before you write any production code, you have to start with a failing test. A test represents a behavior you want to implement

2. Green - Make the failing test pass. In this phase, your task is to make the failing test pass by writing production code. A passing test will ensure that the business requirement is implemented as expected

3. Refactor - Improve the design: Here you need to refactor your code - including your tests as well - while ensuring that you don’t break any existing functionality. In the refactor phase you grow the design by practicing continuous refactoring and do things like:

   • Use proper namings

   • Remove duplication

   • Abstract away business logic

   • Fix common code smells

   • Apply design pattern

2. Learn the three laws of TDD

Practicing TDD effectively requires more than just following the TDD cycle. The key is also applying the three laws of TDD, introduced by Uncle Bob. These laws help you focus on one change at a time and encourage taking baby steps.

The three laws are the following:

1. Always start with a failing test

2. Stop writing your failing test once it fails, and compilation failure is also a failure

3. Stop writing production code once you made the test pass

The TDD flow

The TDD flow combines the TDD cycle with the three laws. Here's a step-by-step visual showing how they work together:

3. Get started with Kata exercises

Greatness comes from practicing. Katas are short (15-30 min) coding exercises that help developers focus on specific skills without the complexity of a real project. They're language-agnostic, so you can use any language you prefer.

Katas are a great way to master TDD fundamentals. Pick one, and start practicing the TDD flow! You can find many Katas here:

• TDD Manifesto

• Awesome Katas

• Coding Dojo

4. Apply TDD on a real-life project

After practicing Katas and sharpening your skills, it's time to apply TDD to real-life projects. Here are some tips to get started:

1. Understand the Requirements: Ensure you have a clear understanding of what you're building before writing tests.

2. Start Small: Begin with a failing test for a simple function or class. Avoid tackling complex features right away.

3. Follow the TDD Cycle: Stick to the rhythm of writing tests, making them pass, and refactoring.

4. Remember the Three Laws: Keep the three laws of TDD in mind to ensure you take small steps

Applying TDD to real projects can feel challenging at first, but starting small will set you up for success.

5. Master clean code and testing

The hard truth is that knowing the rules of TDD isn’t enough to practice it effectively. To truly excel, you need solid testing practices like:

1. Understanding the 5 test doubles: Learn how to use stubs, mocks, fakes, spies, and dummies effectively to test complex interactions.

2. Knowing the most common test smells: Recognize issues like overly complex setups, fragile tests, and missing assertions, and know how to fix them

3. Writing clean and easily maintainable test: Create tests that are easy to read, reliable, and adaptable to change.

Building these skills will help you unlock the full potential of TDD.

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Conclusion

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