demonstrate designing a software or product entity using TDD as a design approach.

Considered as one of the out-of-the-box design approaches, Test-Driven Development (TDD) is often used by expert Scrum developers to design software or product entities. TDD primarily advocates the use of software testing to drive the design process. It primarily includes a cycle of continuously adding tests that define desired improvements or new functionalities.

Effective Implementation of TDD:

The implementation of TDD includes an iterative process often termed as the Red-Green-Refactor cycle.

1. Red: Write a small piece of test that does not pass, and potentially fails to compile at the first stage.
2. Green: Write just enough code to make the test pass merely to affirm that the functionality works as expected.
3. Refactor: Cleanup the code while checking regularly (re-running the tests) to affirm that it behaves exactly as specified.

Discussion:

The unique aspect of TDD lies in the fact that it encourages developers to think through their design before they begin coding, thus leading to a more clear and lean design. Every aspect of the software, including the features and aspects that can be broken or prone to regression, is first covered by a test. This not only ensures the quality of the product but also acts as a form of documentation for how components of a system operate.

The Benefits of TDD:

Some of the major advantages of TDD as a design approach are:

• Improved quality: The frequent iteration of test writing and code correction enhances the overall quality of the software.
• Simplified debugging: Given that tests are written before the actual implementation, debugging becomes a lot easier.
• Enhanced reliability: As tests are done beforehand, the software components become more reliable.
• Documentation: As tests are done earlier, it clearly documents what the software is designed to do.

Simple Illustration of TDD:

Consider a simple scenario where developers are tasked with designing a login function.

Step 1: The developers would initiate writing a failing test case stating the expectations for the designed ‘login’ function.

Step 2: Minimal code would be developed to pass this test case.

Step 3: Code refactoring will take place to eliminate redundancy, with tests repeatedly run to ensure there are no performance breaks in the software.

TDD is an integral part of scoring good grades in the Advanced Certified Scrum Developer (A-CSD) exam. Understanding the mechanism of TDD and how to practically apply it in real-life scenarios can highly enhance a candidate’s command over software designing skills and practicality, thereby further increasing the chances of achieving the certification.

The constant iterative process of TDD brings a sense of discipline regarding maintaining the code quality and robustness. Especially in the context of Scrum methodology, where changes are often abrupt and dynamic, incorporating TDD as a design approach can highly enhance the performance of the developed software entity. Thus, those preparing for advanced Scrum certifications must pay adequate attention to fully understanding TDD.

Final Remarks:

While TDD might seem a bit challenging to get a hang of initially due to the inversion of traditional programming techniques, the long-term benefits it yields are immense. It assists in minimizing tech debt, reducing time spent on debugging, and ultimately helps in delivering a robust and well-built software product. It’s one of many valuable tools available to Scrum developers and must be looked upon as an advantageous investment for the future.