Introduction

The evolution of agile practise has paved the way for more excellent development approaches for faster delivery of high-quality software. Test Driven Development (TDD) is one of the results of such evolution, as it provides a wholesome approach. In the Test Driven Development process, the software development team first creates and tests the developed code for each small app functionality. If the test fails, new code is written to pass the tests, simplifying and sanitizing the code in the process. The TDD framework allows software engineers to write code whenever the automated test breaks, avoid code duplication and improve the code quality.

The basic goal of Test Driven Development (TDD) is to write code and guarantee that the failing tests are fixed before moving on to new code i.e., to write and run automated unit tests before moving on to actual app development. TDD is an excellent example of agile model-driven development since it covers a series of processes starting with extreme programming, unit test creation, and refactoring code, all with the goal of creating long-term robust code. Let’s take a closer look at the important phases of the Test Driven Development process (TDD process).

How does TDD differ from traditional testing?

TDD approach is primarily a specification technique. It ensures that your source code is thoroughly tested at the confirmatory level. Here is how it is different from traditional testing:

Successful tests in traditional testing uncover multiple defects. If a test fails in TDD, it indicates progress because it assures that there is a problem that needs to be addressed.

TDD ensures comprehensive test coverage, which means that every line of code is examined, but it is not the same as traditional testing.

The TDD cycle starts with writing tests to cover a specific change, then developing code to pass those tests, and then refactoring the code as needed before writing new tests. In traditional testing, you develop the whole code first, then run the appropriate tests.

TDD focuses on the production code that verifies that the testing will work as expected. In traditional testing, the team concentrates more on the test case design.

There are three key phases of Test Driven Development:

1. Creating precise tests: Software engineers create specific unit tests to test specific features to ensure they are working properly. Most tests fail, thus, software engineers make sure that the tests are compliant and execute smoothly in order to pass the failing unit test. The developers recognize these test failures based on their assumptions about how a product would behave.

2. Code Correction: Code fails happen often, and the developers need to correct the code with minimal code changes to make test re-execution successful.

3. Code Refactor: After the developer performs successful tests and identifies any redundancy, he optimizes the code to improve overall performance. Developers should ensure that the code refactoring does not affect the program’s external behavior while restructuring the code. A high-level TDD process looks like this:

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  ^{Source:guru99} 

 

What is the Red, Green, Refactor approach in Test Driven Development?

Developers frequently use the Red-Green-Refactor technique to generate test suites, create implementation code, and enrich their code base for a shorter development cycle. As a result, this strategy is divided into three phases:

Unit testing technologies that allow TDD, such as SUnit, commonly use the red-green-refactor phrase. It’s a cycle in which test results are assigned a colour code to each phase. For example, red indicates a test fail, and green indicates a test pass. 

Red Phase: The developers must decide what to build during the Red Phase. This cycle begins with this point. The main purpose of this phase is to create tests that will trigger feature implementation tests. Once the given standards are reached, the test passes. For example, you can execute a test to see if the function sortArray sorts the given values in ascending order with the input value [2,4,1] and the output [1,2,4]. As a result, the expected error message while executing the test would be:

^{Source:Codecademy}

You may now view the message in red. So you define what you want to implement in the red phase. The red error shows your approach towards it.

Green Phase: In Green Phase, the decision regarding figuring out the ways to implement code to make the tests pass. Here, you focus on the solution rather than the optimization. Let’s take the same example as above. You can approach this by writing a loop that repeats over the array, moving the present number over in case it is larger than the number on the right until the array is sorted, like [ 3,4,5,6,2,1]. Below is how the pass message looks like in green after implementation. After this, you may proceed with refactoring/ code optimization.

 

Refactor Phase: Refactor Phase is all about improving the existing implementation or in other words, revitalizing the existing design. In this phase, you are still in green but can think of more ways to enhance and improve the code. Refactoring your test suite always depends on a good test. You can solve the problem above by discovering a much faster approach to achieve the same result with faster code. You can compare and contrast different sorting methods to see which one produces the best results. While refactoring, if the test indicates that something is wrong with the implementation and the output is incorrect, you can re-run the suite after the refactor is complete and expect the following output:

Please note that the test code ran faster (7 milliseconds) after optimization (in the Refactor phase) than in the green phase (19 milliseconds). It is because refactoring the codebase significantly improved the speed of the test suite, increasing the likelihood of producing much more reliable and fast software.

How to perform TDD Test?

By now, we understand that Test Driven Development (TDD) is an approach in which tests are written before writing the code. Below is the standard process flow showing how the TDD Test runs:

1. Add a test.
2. Run all tests and check for test fails.
3. Write code.
4. Run tests.
5. Refactor code base.
6. Repeat the process.

 ^{Source: https://www.andplus.com/blog/test-driven-development}

Detailed description of the steps in the above diagram:

a. Before developing code, create a use case for the software unit you want to create. In the case of behavioral verification statements, creating use cases is easier. In the above example, When the user hits the Convert to Celsius button on the given input Temperature, the conversion field changes to 0°C.

b. Before developing any implementation code for the use case, write a unit test for it. Then see if the code succeeds or fails. The catch is that it must fail at first and if it does not, you may be duplicating existing code, indicating that something is wrong with it.

c.  Now, write the sufficient code to pass the test, nothing more. Only when the test passes consistently, you can move to the stage of writing a new test case for the next use case.

 d. As previously, you write a test for a new use case in this phase. You discover at this stage that a test suite is being created that grows with the software and covers a large amount of executable code.

e. At this point, create enough code to pass all current tests as well as the new one.

f. Refactor your code as needed and clean up the code base.

g. Repeat steps (d) through (e) until your task is complete.

Benefits of Test Driven Development (TDD)

TDD is a balanced software development approach related to coding, testing and designing. It streamlines the development process making the entire process efficient based on the feedback and in the end you get a clean code. Let us discuss some of the advantages of TDD below:

• Modular Principle: In TDD approach, the development team writes tests for smaller features making them strong in learning about the modular design principles. This enables them to go deeper into the architecture of the application and detect problems much earlier.
• Easy Maintenance:  TDD makes refactoring a lot easier. The TDD tests cover all functionalities making it easy to detect any error that might be introduced due to code changes when unit tests begin to fail. So, the developers confidently make changes whenever they revisit the older code version. When code is made for specific functionalities, there are less chances that any code changes would impact the entire code structure. This decreases the chances of any risk of breaking the other parts of the code. So, with efficient maintenance and early error detection, even the cost of the project declines.
• Maximum Test Coverage:  With successful TDD implementation, there are chances of each test covering each functionality, implying maximum test coverage.
• Documenting Code: If you give instinctive names to the unit tests, the future developers quickly understand which test is for what purpose and relates to which code. TDD ensures that the production code exists along with its respective tests. It also reduces the need for over-coding and that only enough production code is written to make the unit tests fail. The tests serve as the documentation.
• Requirement Clarity: The team defines each functionality clearly and comprehensively in the TDD approach before the team starts writing any test.
• Team Collaboration: As mentioned earlier, the XP (extreme programming) principle of TDD ensures the team-based collaborative efforts in the development and test process. This means that any team member can work on the other team member’s code.
• Improved Code quality: You write code with the aim to cause the tests to pass. Additionally, refactoring the code after each test ends provides a clean and optimized code.
• It helps receive Faster Feedback: Due to late feedback, TDD relies on a shorter feedback loop. It is the most significant advantage of test driven development (TDD). Creating one failing test, getting the code to work, and then fixing it all leads to faster feedback. This breaks down a larger problem into smaller chunks in order to give a faster feedback loop. Because of the late feedback, modifications may be heaped on top of broken code, leaving no evident underlying cause. TDD, on the other hand, delivers immediate feedback!  Immediate feedback prevents any such problems by providing timely notifications of the possibility of bugs.
• Identifies and solve problems early and quickly
• Supports cleaner user interface
• Reduction in Bugs and development costs
• Gives flexibility and confidence to developers to make the main application architecture while adding any new functionality
• TDD helps in creating flexible, maintainable and extensible code

How does TDD fit into agile development?

Agile software development always needs a constant feedback loop to get the desired end product which means it is completely feedback-driven. The project requirements keep changing amidst the development cycle, so to keep up with the dynamics, a continuous feedback cycle is needed to avoid any hindrance. The good news is that TDD is fit to handle such changing needs early-on and the test-first TDD approach mitigates any critical hurdles that hinder the software development progress and gets hold of quality and delivery of the product.

Agile’s Extreme Programming (XP) gave rise to unit tests and TDD. The XP technique allows Java Developers to write, add, edit, delete features quickly and efficiently, and verify whether everything operates properly.

It is the consistent feedback, bug fixes and new feature addition, team collaboration (Development+QA+Client) combined to ensure that everything works well as intended. Additionally, when the tests are created well in advance, the teams get to spend their time on many valuable tasks rather than on re-creation of extensive scripts.

Difference between acceptance TDD and Developer TDD

What is Acceptance TDD (Acceptance Test Driven Development) ?

Before moving on to finding the difference between acceptance TDD and Developer TDD, let’s understand Acceptance TDD briefly.

In Acceptance Test-Driven Development technique, a single acceptance test is written from the user point of view which fulfills the requirement of the specification. After this step, write production code that is just enough to fulfill the acceptance test. It is very similar to Behavior TDD. However, the key difference between BDD and ATDD is that BDD focuses on the feature behavior whereas, acceptance driven development captures the accurate requirements. Acceptance TDD checks whether the code is working as expected or not. 

Acceptance TDD encourages team collaboration. The developers, testers, and users commonly define the acceptance criteria. Let’s have a look at the key practices in ATDD:

– To evaluate the real world scenarios
– Finalize acceptance criteria for those test scenarios
– Automate the acceptance test cases
– Focus on the development of those cases

Benefits of ATDD

– Clear and focused Requirement analysis
– Team Collaboration
– Acceptance TDD leads the entire development process

Let’s have a look at the key differences between the two:

Parameters	Developer TDD	Acceptance TDD
Definition	This is a development technique that focuses on implementation of individual units of a desired feature.	ATDD technique focuses on requirement capturing and meeting the needs of the user.
Contributors	Developers	Developers, customers and QAs
Languages used	It uses the same language as used in developing the feature like JAVA, PYTHON, etc.	Gherkin (Simple English)
Focus	Writing Unit Tests	Writing Acceptance Tests
Tools Used	Any open source tools. Junit, TestNG, NUnit frameworks, Selenium tool, Cucumber, BeanSpec, JDave,  JBehave, Spec Flow, BeanSpec, Gherkin Concordian, FitNesse.	TestNG, FitNesse, Thucydides, EasyB, Spectacular, Concordian, Robot Framework, FIT
Understanding tests	Developers mostly write the tests and write for developers themselves.	Tests are easier to understand and are mostly written for any individual to understand.
Bugs	Reduction in the bugs, easier to identify any issues	Bugs in this case could be difficult to identify as compared to TDD.
Suitability	Suitable For those projects that do not have end-users, like API, servers, etc. scenario.	ATDD is suitable in the projects where end user is the key, customer experience is most important, and there is a high level of competition, like in the case of e-commerce applications.

By digging deeper into the above methods can make the decision of the developers and other teams involved in the development cycle to decide which test strategy would be most appropriate for them. The right mix of methods can help attain specific results efficiently.

    ^{Source: https://www.guru99.com/test-driven-development.html}

Conclusion

Traditional development methods have been modified by Agile. Test-driven development is quickly becoming the most favored development method among programmers. It is one of the most valuable techniques because of its several advantages, including early bug discovery, improved code quality, faster feedback, time and cost savings, clean code, and consistent end product quality. Businesses have been able to easily upgrade their software whenever unforeseen business changes occur, with the help of TDD. An organization’s success is determined on its ability to respond quickly to changing business environments. Is TDD, however, worthwhile? There is no one approach to designing custom software, but with the right methodology and mix of development techniques, one can achieve great results.be it for big dominant billion dollar companies or small companies figuring out how to make their apps bug-free. But having a plan B and C is always better than to be at the mercy of technology and apps.