Managing Technical Debt: The Challenges Of Defects In Agile

Technical debt refers to the implied cost of additional rework caused by choosing an easy software solution now instead of using a better approach that would take longer. In Agile development, technical debt accumulates through defects that are known but not fixed right away.

Defects are flaws in the software that cause it to produce incorrect or unexpected results. They range in severity from minor issues to critical bugs that crash the application. Defect debt comes from allowing known defects to remain in the code without fixing them.

The Challenge of Undetected Defects

The biggest contributor to defect debt is defects that remain undetected. Agile methods emphasize working software over comprehensive documentation, so there may not be specifications for what the system should do in all cases. Automated tests only cover programmatically verifiable requirements.

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Some defects escape testing and QA processes and lurk unseen in production. These defects silently accrue technical debt because the development team is unaware of the need to fix them. Each undetected defect represents a technical debt that will have to be paid back later.

Consequences of Unmanaged Defect Debt

Allowing substantial defect debt to build up has several negative consequences:

Increased Costs Over Time

It becomes exponentially more expensive to fix defects the longer they persist. A defect introduced early can incur significant costs down the road after many parts of the system have come to rely on the defective component.

legacy defects require rediscovering context that may no longer be obvious. The original developers who could easily fix it may no longer work on the project. Manual testing and fixes have to redo integration and regression testing that automated systems would have checked.

Lower Software Quality

Unfixed defects directly reduce the quality of the software and user experience. They result in incorrect calculations, UI problems, crashes, distorted data, performance issues, and other problems that disappoint users.

Low quality software loses the trust of users. This drives away potential customers and cuts into market share for a product. The market reputation of the organization itself can suffer from releasing and maintaining low quality software.

Slower Feature Delivery

Carrying excessive defect debt causes teams to slow down delivering new features. Detecting and diagnosing unseen legacy defects introduces unplanned work that delays completing user stories and new functionality.

Testing cycles take longer as existing issues mask other problems. Lengthy tests reduce developer productivity while they wait for answers. New changes often interact with dormant defects to cause unexpected regressions, requiring rollbacks and rework.

Strategies for Managing Defect Debt

Organizations can employ several strategies to avoid accumulating major defect debt:

Automated Testing

Automated test suites exercise application components programmatically without manual intervention. Unit tests verify individual classes and functions. Integration and system tests validate interactions between all parts.

Test automation provides rapid feedback on the correctness and quality of code. Tests pinpoint scope and origin of detected defects. Running test suites during continuous integration catches issues early before they become debt.

Code Reviews and Static Analysis

Manual code inspections uncover problems missed in testing. Modern tools perform static analysis on source code and configurations to detect bugs, security flaws, performance issues, and noncompliant coding practices.

Regular peer reviews keep all developers aware of changes that introduce defects. Addressing issues found during reviews avoids compounding existing debt across versions.

Prioritizing Fixing Known Issues

Using standard Agile practices to prioritize and schedule work helps ensure known defects get fixed:

Add known defects into the backlog tracking system
Include defect remediation efforts in story point estimates
Allocate time to address defects during each sprint iteration

Building fix tasks into the normal workflow eliminates the friction of separate defect tracking systems. Product owners can prioritize technical debt paydown work alongside new capabilities requested by the business.

Technical Debt Tracking

Recording technical debt allows quantification of the liability carried on team velocity. Capturing principle, interest probability, and fixes over time provides data to help manage debt paydown.

By spotlighting increasing levels of accrued debt, tracking mechanics inform decisions on when to slow feature development for comprehensive fixes that remove large amounts of legacy debt.

Balancing New Features and Paying Down Defect Debt

Paying down defect debt competes for resources along with implementing new features. Lack of developer time represents the key tradeoff teams face between technical debt reduction and feature development.

Fixing legacy defects pulls available effort away from delivering new functionality. Paying down debt can stall feature progress to the point that stakeholders see no forward movement week to week.

On the other hand, piling on new features without addressing growing defect debt will cripple long term velocity. If too much unresolved debt accumulates, all productivity eventually goes to identifying, isolating, and managing interactions from legacy defects.

There are no fixed formulas that apply universally. Each team must strike the ideal balance between new features and defect fixes for their context and constraints through continuous inspection and adaptation.

Example Code for Illustration

As an example to demonstrate technical debt principles, consider the following Java code snippet that validates phone numbers:

public boolean isValidPhoneNumber(String phoneNumber) {
    return phoneNumber.matches("[0-9]{10}");
}

This function has a major defect – it verifies 10 digits but does not actually guarantee the input looks like a valid phone number. However, it was quick and easy to implement early on.

Over time, invalid numbers get into the system leading to bugs in applications relying on clean phone data. Attempts to reuse this component cause mysterious issues popping up unpredictably. As technical debt, it incurs growing interest costs in wasted developer time tracking down problems caused by bad numbers.

To fix the defect properly requires updating all callers, adding parameter checks, expanding test cases, and handling all downstream dependencies on this function’s behavior. Each application relying on this component risks quality issues until technical debt gets paid down.

Key Takeaways on Managing Technical Debt

Effective management of defects and technical debt in Agile development boils down to a few key points:

Unseen defects create silent debt through unfixed bugs accumulating over time
Legacy defects exponentially raise costs and complications to address
Proactive testing, reviews, and prioritization limit accruing defect debt
Teams must strike a sustainable cadence balancing new features and fixing defects

Careful management of defects minimizes building up debilitating technical debt. This helps Agile teams maintain velocity delivering high-quality software matched to user needs.