Test Driven Development (TDD) : What, when, how and why.

Test Driven Development (TDD) is a software development approach that emphasises automated tests before writing the actual code. It is a technique where developers write small, specific tests for a particular piece of code before writing that code. This approach helps to ensure that the code being developed meets the requirements and specifications and is free from defects.

Why TDD?

TDD is a powerful tool for software development for several reasons:

  1. Ensures quality: With TDD, developers write automated tests for their code, ensuring it meets the specifications and requirements. It also helps catch bugs early in the development cycle.
  2. Increases productivity: TDD allows developers to catch bugs and issues early in the development cycle, saving time in the long run. With TDD, developers can develop code faster and with higher quality, increasing productivity.
  3. Reduces costs: By catching bugs early in the development cycle, TDD reduces the cost of fixing those bugs later. This helps to reduce overall development costs and helps to ensure that the project is completed on time and within budget.

When is TDD not suitable?

While TDD is a powerful tool, it may not always suit every project. TDD may not be the best approach in the following scenarios:

  1. Limited resources: TDD requires significant resources to develop and maintain automated tests. If resources are limited, TDD may not be the best approach.
  2. Small projects: TDD may not be the most efficient approach for small projects as it may take longer to develop automated tests than to write the actual code.
  3. Complex projects: TDD may not be suitable for complex projects with many interdependencies and interfaces. It may not be easy to write automated tests for such projects.

Software development Steps for TDD

The TDD process involves the following steps:

  1. Write a test: The developer writes an automated test that fails, indicating that the code to be developed does not meet the specifications.
  2. Write the code: The developer writes the code to pass the test.
  3. Refactor the code: The developer refactors the code to ensure it is efficient and meets the requirements.
  4. Run the tests: The developer runs the automated tests to ensure the code meets the requirements and specifications.
  5. Repeat: The developer repeats the process, writing a new test and code until all the requirements are met.


TDD is a powerful approach to software development that emphasizes writing automated tests before writing code. TDD ensures quality, increases productivity and reduces costs. While TDD may not be suitable for every project, it is a powerful tool for projects where it is suitable. The TDD process involves writing a test, writing the code, refactoring the code, running the tests, and repeating the process until all the requirements are met.

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