Test Driven Development

Zoltan Fehervari

August 23, 2023

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Looking to improve code quality, maintainability, or team collaboration? Discover how Test Driven Development (TDD) can be your ally in 2023!


Test Driven Development (TDD) is no stranger to anyone in the software development dimension. But what does TDD mean, exactly, and how relevant is it in 2023? This article aims to delve into the ever-evolving concept of TDD, its approaches, examples, and relevance, particularly in Agile and Java environments. Understanding how TDD complements our Testing Pyramid or integrates with Shift-Left Testing can help us grasp its current and future significance.

What Does TDD Mean?

TDD stands for Test Driven Development. It is a software development methodology focusing on writing automated tests before any production code. To put it succinctly, it’s a test-first development approach where you write a test that defines a function or improvements of a function, which should be very succinct.

How TDD Works: Red, Green, Refactor

Understanding TDD is to understand its mantra: "Red, Green, Refactor."


Write a failing test. This serves as a specification for what the code should do.


Write the minimum code necessary to pass the test.


Refactor the code while keeping it functional.

Test driven development steps - Bluebird

Testing Development: The Steps of TDD

  1. 1
    Write a test
  2. 2
    Run the test (it should fail, showing that the function is not yet implemented)
  3. 3
    Write the code to make the test pass
  4. 4
    Run tests
  5. 5
  6. 6

The approach keeps your codebase clean while ensuring it performs the expected functions. It's a vital part of Agile development methodologies.

Why Choose TDD?

Choosing TDD means choosing quality, maintainability, and efficiency. It integrates exceptionally well with Agile methodologies and is gaining popularity in 2023. TDD allows developers to:

  • Write better quality code

  • Unearth issues early

  • Ensure overall project success

Challenges and Criticisms of TDD

While TDD has its merits, it is essential to acknowledge its limitations and criticisms. The methodology demands a significant initial time investment and has a steep learning curve for newcomers. Moreover, TDD may not be well-suited for all kinds of projects, especially those that are more exploratory in nature and lack well-defined specifications.

Tools and Libraries

In the Java and Agile contexts, several tools and libraries can facilitate TDD. JUnit is perhaps the most popular testing framework used in Java for this purpose. Additionally, mocking libraries like Mockito prove invaluable for simulating conditions and scenarios that are challenging to produce during testing.

Test driven development - Bluebird

Best Practices

Effective TDD requires adhering to some best practices. Firstly, tests should be simple and focus on a single aspect of the code. Secondly, the time to refactor is after the code passes all the tests. Lastly, comprehensive documentation should accompany the tests and the code, explaining why certain tests exist and the reasoning behind the implemented solutions.

TDD Examples

Examples make everything clearer, right? Let's consider TDD in Java, keeping in mind our past discussions on Java Testing Frameworks.

Example: Simple Addition Function in Java

  1. 1
    Write Test: Write a test to check the addition of two numbers.
  2. 2
    Run Test: The test will fail (Red).
  3. 3
    Write Code: Implement the addition function.
  4. 4
    Run Test: The test passes (Green).
  5. 5
    Refactor: Optimize code if necessary.

TDD and Agile

As stated earlier, TDD works exceptionally well in Agile environments. Why? Because Agile is all about iteration, feedback, and rapid development—things TDD is excellent at facilitating. Our previous article about Software Testing Trends shows how Agile and TDD are key modern trends.

How TDD Complements Other Testing Approaches

TDD serves as the initial layer of your testing pyramid. It takes care of the unit testing part, allowing higher levels of testing, like Penetration Testing, to focus on broader system behavior.


Test Driven Development is not just about writing tests; it's a methodology that governs your entire software development cycle, ensuring quality, reliability, and maintainability. As software becomes more complex and the need for reliable code increases, TDD is likely to become even more crucial.

Whether you are looking to improve code quality, maintainability, or collaboration among your team, Test Driven Development offers a time-tested methodology.

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