What is Test-Driven Development (TDD)? TDD Approach, Cycle, and Rules

What is Test-Driven Development (TDD)? TDD Approach, Cycle, and Rules

Software testing is the most crucial part of any software development project. When a comprehensive and robust software testing suite is executed, then several bugs, mistakes, and incorrect assumptions are found. These mistakes in the software are definitely made by the human being who developed the code. So, by using different types of software testing methods like unit and integration testing to user interface and regression testing, you can release final high-quality software. However, in most cases, the development team struggles to meet the pressure of deadlines and budget limitations. As a result, they run short of time to serve for executing the software test. In order to counteract this system, software developers introduced the concept of TDD (Test Driven Development). The article below will provide an in-depth understanding of the test-driven development approach, its cycle, and the rules of TDD.

1. What Is Test-Driven Development?

TDD is an acronym for Test-Driven Development and a buzzword used in the tech industry. As the name suggests, the concept relates to the development methodology where before writing a piece of code, we first write tests that will verify compliance with the code.
Basically, TDD works on short cycles of repetitions, where each feature of a test system is created before. This new test is likely to be a failure because we do not have to implement the functionality in question first hand; instead, we write cases and then implement the functionality to make the test pass! That’s simple!

TDD is also known to be calm, yet a minor samurai – not so fast! This means that we cannot just write another test just because we already have a passing test, i.e., we need first to refactor the feature we just wrote, that is, it must go through a small bath of “good practice” Software Development. These good practices ensure software with cleaner, cohesive, and less coupled code.

2. Test-Driven Development Cycle – “Red, Green, Refactor”


TDD is based on the preceding rules and allows for the next development cycle, which goes by Red>Green>Refactor

Red: Initial stage of the TDD, where you write a test that fails for some functionality you will still write.
Green: Already created with the test, is the time you need to pass the test, always remembering to go for the simplest solution first.
Refactor: Step to eliminate redundant codes, remove couplings and make the code a more readable design.

How To Do Test-Driven Development?

Now, the main idea about the test-driven development approach is pretty clear. Here is how you can implement TDD in software development projects.

  • Create the Test: The first step to implementing TDD is creating the unit test that evaluates a significant part of your codebase. The tester can get inspiration for writing tests in TDD that can be drawn from use case diagrams and user stories.
  • Use case diagrams to define how a system should behave to activities the user performs.
  • While User Stories are detailed text descriptions of the software requirements specified by the project stakeholders.
  • Run the Test: When you execute your unit testing suite, you will receive an arrow while compilation explaining that the class does not exist. This message’s information will tell the developers how to resolve the issue. However, in some cases, this type of error will be detected during the runtime rather than at the time of compilation. Moreover, with the help of assert statements, you can verify that a given condition is true while executing the code or not. There is also the option of throwing an exception to check for one or more error conditions. And so on, the TDD process continues, and several additional test cases are also added to end the unit testing suite. Furthermore, each unit test in TDD is independent of other entities in TDD, i.e., no test depends on the behavior of other tests running.
  • Fix the Code’s Detected Issues: If the developers obtain appropriate messages in hand, then it becomes far easier for them to fix the problems. So, your primary focus should be on writing a solution that satisfies the test conditions rather than focusing on writing a perfect solution.
  • Rerun the test after fixing issues: Once you feel confident that all the issues are resolved, then you have to rerun the testing suite to see whether issues are actually removed. If everything is pretty good in this test, you are following the TDD, and you can move further operations.
  • Refactor the Code: It is an optional step, where you will refactor the code that you wrote to integrate it with the existing codebase. This step is performed to make the code more readable, separating it into logical parts and redefining different moving variables and methods.
  • Repeat: TDD cycle continues and results in expansion of features and functionalities of the software. At times when you find that TDD can’t easily pass a new test, or you break previous tests with new written codes. Then in such cases, the best solution to TDD is usually to revert the change you made. It saves your time from wasting on a lengthy debugging process.

What Are The Rules Of TDD?

Rules Of TDD
The operation in TDD mode imposes the following four rules:

First Rule: Always write the test before writing the code of the tested method.

You should not write the target implementation code as you have not written the code for the associated test. That is, it is necessary to have imposed the contract before entering the target code.

Second Rule: Set in the test behavior and expected results of the test method.

The test code requires compliance with the business rule. Determine the expected result of the test code as the implementation code for the test does not exist or is not compiled yet.

Third Rule: Simplify implementation code and make sure that passing the test is a success.

The implementation code should be simple in order to increase efficiency. This is why it is necessary to rewrite the code after all tests are successful. Furthermore, the tests must remain in success at the end of rewriting the code.

Fourth Law: The coverage of the tested code is 100%.

100% coverage of the code allows us to avoid unnecessary or untested code that can be misleading.

To Conclude:

The developers perform this cycle at each change in the application code. Continuous integration validates that the implementation code always respects contracts imposed by the tests. Clustox offers both Test-Driven Development and Behavior Driven Development. You can contact us for both services.
For more information on TDD, stay tuned in!

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