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TDD: How to Perform, Best Practices, and Examples

TDD Bestpractices
Posted On: 2 November 2023

Test-Driven Development (TDD). With its unique phases and behaviors, this technique has altered how developers approach coding. In this installment of our TDD examination, we'll go through its basic development cycle, practical techniques for implementation, and real-world examples from web, mobile, and embedded applications. We'll also discuss how ACCELQ is shaping the future of test automation along the way.

Test-Driven Development Cycle of Software Development

The TDD process involves three phases of the software development cycle: The Red, Green, and Refactor (Blue) phases. Let’s understand how each phase works in the following sections:

Understanding TDD Concepts

Red Phase (Write a Failing Test):

In this initial phase, developers create a test defining the desired behavior without implementing code. This test often won't compile, hence the name "Red Phase."

Green Phase (Write Code to Pass the Test):

The focus here is on writing the simplest code necessary to make the test pass. Developers aim to find a working solution, even if it means ignoring coding best practices and performance considerations temporarily.

Refactor Phase (Improve Code Without Changing Functionality):

In the Refactor or "Blue Phase," the code is refined while maintaining passing tests. This is when developers can address design patterns, code quality, and readability. The test suite continually verifies that functionality remains intact, serving as a safety net.

These three phases, when repeated iteratively, lead to the development of high-quality, well-tested code.

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How to Perform The TDD Test?

Step 1 – Write a Test:

  • Begin by creating a specific test case that describes the desired behavior of your code. This test should be crafted before writing any actual code.
  • Employ a testing framework suitable for your programming language (e.g., JUnit for Java, pytest for Python) to build the test.
  • Make sure the test is concise and concentrates on a single piece of functionality. It should contain checks (assertions) to validate the expected behavior.
  • Initially, this test will fail as no code fulfills its requirements. This is an essential part of the process and verifies that the test functions correctly.

Step 2 – Run the Test:

  • Execute the test using your chosen testing framework. It is expected to fail since the code to implement the functionality hasn’t been created yet.
  • The failure confirms that the test effectively assesses the desired behavior currently absent in the code.

Step 3 – Write the Code:

  • Now, you can begin writing the code necessary to pass the test. Concentrate on writing the minimum code essential to meet the test case requirements.
  • In this step, avoid trying to build the complete feature. Instead, aim to write only what’s needed for the test to pass successfully.
  • While the code should follow coding standards and be clean, you can temporarily overlook certain optimizations or best practices.

Step 4 – Run All Tests:

  • After writing the code, run all the tests in your suite, including the one you crafted in Step 1 and any pre-existing tests.
  • This step confirms that the new code hasn’t unintentionally broken any existing functionality. If any test fails, it indicates a regression issue.

Step 5 – Refactor:

  • In the final step, focus on improving the code’s design, maintainability, and readability without altering its external behavior.
  • Concentrate on removing redundancy, enhancing variable naming, and adhering to best coding practices.
  • Ensure that all the tests continue to pass as you refactor. If a test fails during this process, the changes introduce a problem.

You incrementally develop your codebase by consistently following these steps in a repetitive cycle (Red-Green-Refactor). This approach allows you to add new functionality while upholding strong test coverage and code quality, resulting in robust and maintainable software.

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Examples of TDD Implementation

As you now have a fair idea about what TDD is in software development, here we have given some examples of TDD in actions with some simple scenarios.

Let’s go through them all quickly!

Simple web application development using TDD

Step:1 - Write a failing test:

In the TDD method, the first step is to create a failing test. Here’s the code for that:


import unittest

class TestGreeting(unittest.TestCase):

    def test_greeting(self):
        # TODO: Implement this

if __name__ == '__main__':

Step 2: Run the test:

Running the test initially fails because the required code, in this case, the greeting() function, hasn't been implemented yet.

Step 3: Implement the Minimum Code to Pass the Test

The next step is to write the test with the minimum code required. In this case, it’s a function that returns a basic greeting.

def greeting():
    return "Hello!"

Step 4: Run the Test Again

Running the test again should now pass since the minimal code has been added.

Step 5: Repeat Steps 2-4 Until Completion

You can continue enhancing your web application by adding more features, like personalizing the greeting based on the user's name. For each new feature, start by writing a failing test and then implement the code required to make it pass.

Mobile app development with TDD

Developing a mobile app with TDD follows a similar approach to web development but with some differences due to the complexities of mobile app user interface (UIs) and multi-platform considerations.

Here are the steps for developing a mobile app with TDD:

Step -1: Write a failing Test

Here’s an example with Kotlin:

// TestGreeting.kt

class TestGreeting {

    fun greeting() {
        // TODO: Implement this

Step 2: Run the Test:

As expected, the test fails initially because the greeting() function is missing.

Step 3: Implement the Minimum Code to Pass the Test

Write the minimum code required to pass the test by adding a function that returns a simple greeting.

Here’s the code for that:

fun greeting(): String {
    return "Hello!"

Step 4: Run the Test Again

Now, running the test should pass as you’ve added the minimal code.

Step 5: Repeat Steps 2-4 Until Completion

Continue enhancing your mobile app by writing failing tests for new features and then implementing the code to make them pass.

TDD in embedded systems development

When you decide to have embedded systems development with TDD, it comes with its own unique challenges due to resource constraints and real-time requirements.

Here are the steps to develop embedded systems in TDD:

Step 1: Write a Failing Test

// test_greeting.c


void greeting() {
    // TODO: Implement this

int main() {
    return 0;

Step 4: Run the Test Again

Now, running the test should pass as you’ve added the minimum code required.

Step 5: Repeat Steps 2-4 Until Completion:

Continue improving your embedded system by writing failing tests for new features and then implementing the code needed to make them pass.

In all these development scenarios, TDD helps ensure that your code functions correctly and meets the desired requirements while also making it easier to catch and fix issues early in the development process.

Step 2: Run the Test

Running the test fails initially because the greeting() function hasn't been implemented.

Step 3: Implement the Minimum Code to Pass the Test

Write the minimum code required to pass the test, which, in this case, is a function that returns a simple greeting.

void greeting() {

4 TDD Best Practices For Software Developers

To adhere to the maximum benefits of TDD, follow these best practices:

1.Writing clear and concise test cases:

Test cases should be easy to understand and focused on specific behaviors. Moreover, clear and descriptive test names are essential for clarity.

2. Avoid unnecessary complexity in tests:

Keep tests simple and focused on one functionality aspect to avoid confusion and maintainability issues.

3. Test coverage and continuous integration:

Ensure that the test coverage is comprehensive, covering different code paths. Incorporate continuous integration to run tests on code changes automatically.

4. Test naming conventions and documentation:

Follow consistent naming conventions for tests and document their purpose and expected outcomes.

Get More Insights About Testing Automation From AccelQ Experts

At ACCELQ, we help testers master the art of test automation. With our cloud-based continuous testing platform, testers can seamlessly automate API and web testing without writing a single line of code. This helps them eliminate manual testing and save a lot of time.

Get started and master ACCELQ to have powerful capabilities. Explore a range of our resources at our Academy and achieve the desired growth in your career.

Geosley Andrades

Director, Product Evangelist at ACCELQ

Geosley is a Test Automation Evangelist and Community builder at ACCELQ. Being passionate about continuous learning, Geosley helps ACCELQ with innovative solutions to transform test automation to be simpler, more reliable, and sustainable for the real world.

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