Practical tips for getting started with Test-Driven Development

Start with Simple Tests

Begin with straightforward, easy-to-test methods, such as mathematical calculations or simple data manipulations. This will help you get familiar with writing tests and seeing the Red-Green-Refactor cycle in action without overwhelming complexity. Simple tests are a good way to build confidence and understand the rhythm of TDD.
Embrace the Red-Green-Refactor Cycle

Follow the Red-Green-Refactor steps closely: write a test that fails, write just enough code to make it pass, and then refactor if necessary. Sticking to this cycle keeps you focused and ensures you write only the necessary code to meet the test’s requirements. Avoid the temptation to skip any step, especially the “Red” step, as each one serves an essential purpose.
Keep Tests Small and Focused on One Behaviour

Write tests that check a single behaviour or functionality. This focus helps you understand exactly what’s being tested, makes debugging easier, and aligns with TDD’s goal of isolating units of code. If a method or function has multiple aspects, write separate tests for each one to keep them manageable and precise.
Name Tests Descriptively

Use clear and descriptive names for each test so that anyone reading it understands what is being tested and why. Following a convention like MethodName_StateUnderTest_ExpectedResult (e.g., Add_TwoPositiveNumbers_ReturnsSum) helps make the purpose of each test obvious and improves readability.
Write the Simplest Code to Pass Each Test

In the “Green” stage, write only the minimum code necessary to make the test pass. This keeps you from over-engineering or writing unnecessary code. If a feature requires more complexity, add it gradually by writing additional tests and expanding the code incrementally.
Refactor Frequently

Refactoring is an integral part of TDD, so use this stage to clean up your code, improve readability, and simplify logic. Since tests verify that functionality hasn’t changed, you can refactor with confidence. Small, frequent refactors also keep code clean and maintainable as it evolves.
Use Mocks and Stubs to Isolate Tests

When testing code that relies on external dependencies like databases, APIs, or other services, use mocks or stubs to simulate these dependencies. This isolation keeps your tests focused on the specific functionality and avoids the overhead of setting up complex external systems. In C#, for instance, libraries like Moq make mocking easy.
Don’t Aim for Perfection on the First Try

TDD is an iterative process, so don’t feel pressured to write flawless code immediately. Write the code that makes the test pass, then improve it gradually through refactoring. TDD is as much about refining code over time as it is about achieving functionality.
Run Tests Frequently

Run your tests frequently to catch issues as soon as they occur. Running tests regularly allows you to address problems in small, manageable increments rather than having to trace back through a long series of changes.
Practice Writing Tests for Edge Cases

TDD encourages thinking about different scenarios, including edge cases. Once you’re comfortable with the basics, consider tests that cover scenarios like invalid inputs, boundary values, and unexpected states. This practice improves the robustness of your code and reduces the risk of hidden bugs.
Don’t Let TDD Slow You Down

TDD has a learning curve, and it’s normal for it to feel slow at first. Focus on learning the process and following the Red-Green-Refactor cycle without worrying about speed. With time, TDD will become faster and more natural, and you’ll experience its benefits in catching bugs early and maintaining high-quality code.
Celebrate Small Wins

Completing each test and making it pass is a small victory, so take a moment to appreciate each successful cycle. This positive reinforcement helps build confidence in your TDD skills and makes the process more enjoyable.