Regression Testing – A systematic Approach:

1. Coverage
2. Risk
3. Cost

Evaluate what tests can best address the most important risks with the most coverage given the time, tools and resources.

Understand the Coverage:
1. Start with large areas of coverage
2. Drill down into more focused areas within each of those large areas.
3. Followed by subsequent levels of detail until you get down to specific testable units.

Understand the Risk:
FIBLOTS mnemonic for performance testing works wonderfully for evaluating regression testing risk:
• Frequent: What risks are associated with the most used features?
• Intensive: For the intensive features in the application, what specific constraints are concerning, how the supporting platform or code base changed over time, or how the use changed?
• Business-critical: Which features are most critical to the business or the purpose of the application?
• Legal: What has to be tested because of legal requirements or SLAs?
• Obvious: What will happen if it doesn't work?
• Technically risky: Where's the technical risk and how has it changed over time?
• Stakeholder-mandated: What have been told to test?

Risk and Coverage Together:
Charter the work once the coverage (What to Test) and Risk (Why to Test) are identified.
1. Put all activity together meaningfully.
2. Prioritise the work
3. Evaluate what can realistically cover given the time, tools and resources
4. Review and agreement on coverage.
5. Schedule

Review the Coverage, Risk and Priority periodically.