Development without testing is incomplete; they go hand in hand. Test-driven development is a powerful approach in the transformation of writing code for developers. İn test-driven development, the developers test first and then write the code, making it a better approach towards development.
İn this guide, you will walk through the essentials of Test-Driven development, its advantages and disadvantages, best practices, and stages in software testing. Let’s begin to dive deeper into details!
What is Test-Driven Development?
Test-Driven development (TDD) is a software development method in which tests are written before writing the code. Back in 2003, Kent Beck introduced TDD whose main goal was to write clean code that actually works.
TDD follows a single rule: a code is only changed if any test fails. Otherwise, only refactor to optimize the code. İt is a very short and repetitive development cycle.
In TDD, customers’ requirements are turned into specific test cases, and software is written and improved to pass the new tests. TDD is suitable for both mobile and web app developers.
Test-Driven Development Cycle
Let’s understand the TDD cycle step by step and see how it works. It is also known as the Red-Green-Refractor process.
- Add a Test
First, the developers need to understand the requirements and create a test. This practice separates Test-Driven development from traditional software development methods. Here, the developers focus more on feature specifications than on the code.
- Red Phase
By running tests, you will validate that the new tests are failing with the existing code and new code is required. As the test fails initially, it is the “Red” phase.
- Green Phase
After the red phase, write the minimum code necessary to pass the test. This is the “Green” phase.
- Refactor
As the test is passed, it must be maintained and cleaned up in the following ways:
- Place the test in its logical place in the code.
- Eliminate the duplication.
- Set object definitions and names to represent their purpose.
- Adding more functions can make the code lengthy, so splitting the code can improve readability.
- All the tests re-run throughout the refactoring phase, it is clear that the process does not alter any existing functionality.
- For Adding a New Test, Repeat From Step 1
İf the new code does not satisfy the new test, then revert to a working code. Avoid extensive debugging.
The Test-Driven Development Cycle
Click each phase to explore the Red-Green-Refactor process
👆 Select a Phase
Click on any phase in the cycle above to learn more about that step in the Test-Driven Development process.
TDD follows a simple, repetitive cycle that ensures code quality and functionality through continuous testing and improvement.
Advantages of Test-Driven Development
Test-Driven development builds a strong foundation for your codebase and also offers a lot of advantages to enhance the software development process.
- Enhanced Code Quality
Keeping in mind the requirements and specifications upfront, TDD leads to cleaner and reliable code.
- Reduced Debugging Duration
Test-Driven development defects the bugs in the initial process and saves time , making it easier to solve the issues.
- İmproved Design
TDD encourages developers to write concise and more focused code, leading to a well-maintained codebase.
Limitations of Test-Driven Development
While there are numerous benefits of TDD, there are some disadvantages as well. Let’s have a look at them:
- Complexity
There are chances of writing too many codes or complex tests, leading to a burden of maintenance.
- Time Consumption
Writing down the test before the code can slow down the process of development. This can be more lengthy for new teams.
Test-Driven Development Examples
Let’s see some examples of TDD:
- Calculator Function
İn a calculator function, a TDD approach involves writing a test case for the “subtract” function and then writing the code to pass that test. If the function is working, this can apply to other functions like addition, multiplication, and division.
- E-commerce Website
For an e-commerce setup, a Test-Driven development approach involves writing down the test cases for various features like product listing, shopping cart, and checkout. Tests would be written down to ensure the process works fine at each stage, from adding products to the cart to final checkout.
- User Authentication
İn a user authentication system, a TDD approach would involve writing a test case for user login and then writing the code to pass this functionality. Once the login function works properly, additional test cases will be written for registration, password reset, etc.
Challenges in Test-driven Development
There are two key challenges for the TDD process.
- Mocks and İntegration Tests
Developers need to depend on fakes or mocks when external systems are involved. These tools stimulate real system behaviour to speed up the tests. But these tools may obscure the system behaviour and require additional tests to verify end to end functionality. To overcome this challenge, developers should use fake objects for isolation.
- Code Visibility
When the developers write the test code, it requires the main code. But due to some hidden features like hiding private details this can be complicated. For overcoming this, developers use tricks like reflection or inner classes. These tricks make the design weaker.
To make the final code clean, developers can remove the tricks from the real code by using conditional compilation. They just use tools like reflection in testing, keeping the final code clean and safe.
Best Practices for Test-Driven Development
Test-driven development is a cyclic process of writing a failure test, then writing the minimum code to make the test pass, and then refactoring it. The following are the best practices you should consider while practicing Test-Driven development:
- Understand the Requirements
Before writing the test, make your mind clear about the specifications of the feature you are developing. It helps you write focused tests.
- Write Small Tests
Keep your tests small and simple, and try to address a single aspect of the code. It helps in improving the readability and allows for easy debugging.
- Test for Edge Cases
When designing your tests, you should consider edge cases. They often reveal potential bugs or unexpected behaviour lying at the extreme of the input domain.
- Refactor Regularly
After passing the test, refactor the code and improve the design. It helps you to maintain the code and keep it clean.
- Fast Feedback
Fast feedback allows for faster development and catches the issues earlier to tackle them.
- Automate Your Tests
Utilize test automation and tools to automate the execution of your tests. This ensures consistent and reliable test results and integrates them into your development workflow.
- Follow the Red-Green-Refractor Cycle
Stick to the fundamentals of the TDD cycle of writing a failed test(red), implementing minimum code to pass it(green), and refactoring the code to improve its design( refactor). Repeat the cycle for each test and code.
- Maintain a Comprehensive Test Suite
Create a balance between unit tests, integration tests, and acceptance tests. Each type serves for a different purpose for the code.
- Learn From Test Failures
Whenever a test fails, analyze the failure, identify the cause, and fix the code to clear the issue.
Key Takeaways: Mastering Test-Driven Development
Test-Driven development proves to give a structured approach to software development. It focuses on the specifications of the functions for a higher quality and lower defects. Despite having some challenges like code visibility and mocks integration, TDD is valuable for improved collaborations.
By breaking down software into small, testable units, TDD strengthens developers to make changes confidently. As you have learnt your TDD journey, implement it into your software for more maintainable, reliable, and agile software!
Ready to implement TDD in your software development project? Contact our team. That’s it for now! Stay connected for more updates.
