regression-testing

name	regression-testing
description	Strategic regression testing with test selection, impact analysis, and continuous regression management. Use when verifying fixes don't break existing functionality, planning regression suites, or optimizing test execution for faster feedback.
category	specialized-testing
priority	high
tokenEstimate	1000
agents	["qe-regression-risk-analyzer","qe-test-executor","qe-coverage-analyzer"]
implementation_status	optimized
optimization_version	1
last_optimized	2025-12-02T00:00:00.000Z
dependencies	[]
quick_reference_card	true
tags	["regression","test-selection","impact-analysis","ci-cd","change-based","risk-based"]

Regression Testing

<default_to_action> When verifying changes don't break existing functionality:

1. ANALYZE what changed (git diff, impact analysis)
2. SELECT tests based on change + risk (not everything)
3. RUN in priority order (smoke → selective → full)
4. OPTIMIZE execution (parallel, sharding)
5. MONITOR suite health (flakiness, execution time)

Quick Regression Strategy:

• Per-commit: Smoke + changed code tests (5-10 min)
• Nightly: Extended regression (30-60 min)
• Pre-release: Full regression (2-4 hours)

Critical Success Factors:

• Smart selection catches 90% of regressions in 10% of time
• Flaky tests waste more time than they save
• Every production bug becomes a regression test </default_to_action>

Quick Reference Card

When to Use

• After any code change
• Before release
• After dependency updates
• After environment changes

Regression Types

Type	When	Scope
Corrective	No code change	Full suite
Progressive	New features	Existing + new
Selective	Specific changes	Changed + dependent
Complete	Major refactor	Everything

Test Selection Strategies

Strategy	How	Reduction
Change-based	Git diff analysis	70-90%
Risk-based	Priority by impact	50-70%
Historical	Frequently failing	40-60%
Time-budget	Fixed time window	Variable

---

Change-Based Test Selection

// Analyze changed files and select impacted tests
 (): [] {
   testsToRun =  <>();

   ( file  changedFiles) {
    
    testsToRun.();

    
     dependentTests = testCoverage[file] || [];
    dependentTests.( testsToRun.(t));
  }

   .(testsToRun);
}