Defect Prevention Methods and Techniques

An Effective Approach to Defect Prevention and its Critical Perspectives:

In IT projects, the testing teams are commonly referred to as Quality Assurance.

Beyond the technical aspects, Quality Assurance activities do not only focus on defect identification (which is the process of finding defects after they occur, also known as testing or Quality control), but also include defect prevention (ensuring that defects do not occur in the first place or minimizing their occurrence before the software product is developed).

An equivalent simple equation can be:

QA = QC (defect identification) + Defect prevention

While this may sound simple, there is limited guidance available on how to approach and execute defect prevention tasks.

The truth is, defects detected during the testing phase or worse, after release, are more expensive to fix and can damage the brand’s trust. Therefore, it is crucial to take preventive measures as early as possible. Additionally, defect prevention also contributes to achieving the highest CMMI (Capability Maturity Model Integration) Level for companies.

In this article, let’s delve into defect prevention in more detail.

Defect Prevention

Defect Prevention is a crucial step or activity in any software development process and accounts for approximately half of the testing tasks, as shown in the diagram below:

To summarize, here are the defect prevention responsibilities for testers at each stage:

#1) Review of Requirement Specifications:

After understanding the customer’s requirements, prepare a summary of the requirements.

At this stage, it is important to conduct reviews – the first level of review should be within the team, followed by an external review (by a developer, business analyst, or client) to ensure alignment among all perspectives.

#2) Design Review:

The design stage can be considered a strategic stage, and going through it will provide the QA team with a better understanding of the pros and cons of each strategy.

This critical walkthrough helps uncover any problems with the strategies and allows for their resolution before proceeding. It serves as a feasibility study for the selected strategy/strategies.

#3) Code Review:

Although testers have limited direct involvement in this phase, code review is still conducted. Developers perform code inspections, walkthroughs, and reviews before unit and integration testing the application.

Methods and Techniques for Defect Prevention

Below are some traditional and commonly used methods for defect prevention:

#1) Review and Inspection: This method involves self-checking, peer reviews, and inspection of all work products.

=> For more information on how this process is carried out, please refer to our Test Documentation Reviews article.

#2) Walkthrough: This method is similar to reviews, but it focuses more on comparing the system to the prototype, providing a better understanding of its correctness and/or look-and-feel.

#3) Defect Logging and Documentation: This method involves documenting key information and arguments/parameters that can support defect analysis.

#4) Root Cause Analysis: Root cause analysis encompasses two major approaches:

I) Pareto Analysis:

Pareto analysis is a formal and simple technique that helps prioritize problem resolution for maximum impact. It states that 80% of the problems arise from 20% of the causes.

Identified problems are then prioritized based on frequency, and detailed statistical analysis is performed to determine the 20% of reasons responsible for the 80% of problems. By focusing on these core reasons and eliminating them, results are guaranteed while minimizing the extent of required work.

II) Fishbone Analysis:

Also known as Ishikawa Analysis, this visual root cause analysis technique does not rely on statistics. It is based on team-wide brainstorming. The diagram below provides a better understanding.

The problem is written on the rightmost side, and causes are listed on the horizontal line passing through it. The branch with the most cause-subclause bones (or lines/branches) represents the most serious problem to be eliminated. This technique is also referred to as cause and effect analysis.

TMM Level and Handling Defects by Test Organization

#1) TMM (Testing Maturity Model) is based on CMM (Capability Maturity Model).

#2) Defect Prevention involves the collaborative effort of many staff members at various stages, which is why it plays a prominent role in achieving TMM Level 5. For instance, if a defect occurs frequently in any test case or procedure, the organization may assign a group of staff members to analyze the defect and develop a plan with actions for process changes to address the problem.

#3) Some benefits of the defect prevention program include:

• Motivated and more aware employees
• Improved customer satisfaction
• Increased reliability, manageability, and predictability
• Enhanced continuous process improvement

Team Roles and Responsibilities

The defect prevention process involves three critical groups:

Manager’s Role:

• For the success of any defect prevention program, management must provide strong support.
• Support can manifest in the form of resources, training, and tools necessary for successful implementation of the plan.
• Management should define appropriate policies and be open to cultural changes if necessary.
• Managers should encourage discussions, distribute a common defect list, and promote changes in the process.

Tester’s Role:

• Testers maintain the defect database and ensure that defect data is regularly updated and current.
• They play a role in planning the implementation of changes.

Client’s Role:

• The client’s role is comparatively small, but their commitment to quality is crucial.

Conclusion

Defect Prevention plays a major and crucial role in the software development process. It helps manage the quality of the software product in a timely and cost-effective manner, utilizing the techniques mentioned above.

It ensures that problems are identified and resolved early, before they manifest in the application. Root cause analysis is considered the primary approach for identifying and eliminating issues.

Maintaining software quality is the responsibility of the core management and the entire team, including the project lead, client, and all team members.

What are your methods for defect prevention? Please share your comments, questions, and thoughts below.