regression-testing

regression-testing is a skill for Claude Code from summarybotng/summarybot-ng. It costs 41 tokens per session (1,567 once invoked), scanned A, original, MIT.

A guide for choosing and running tests after code changes to check that existing features still work. Regression testing means checking that a fix or new change has not caused older behaviour to fail.

In plain words
What is it for?
Use it after code or dependency changes, before releases, and when maintaining smoke, selective, extended, or full regression suites.
Why use it?
It avoids rerunning every test unnecessarily while still focusing feedback on changed and risky areas.

Skill for Claude Code

Written for Claude Code: installed under .claude/.

Good fit Use it after code or dependency changes, before releases, and when maintaining smoke, selective, extended, or full regression suites.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/summarybotng/summarybot-ng/regression-testing
Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent
npx skills add summarybotng/summarybot-ng --skill regression-testing
Clone the repo
git clone --depth 1 https://github.com/summarybotng/summarybot-ng

Made for: Claude Code.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for regression-testing

README.md
[![agentmods](https://agentmods.dev/badge/skills/summarybotng/summarybot-ng/regression-testing/github.svg)](https://agentmods.dev/skills/summarybotng/summarybot-ng/regression-testing)
Your own site
<a href="https://agentmods.dev/skills/summarybotng/summarybot-ng/regression-testing"><img src="https://agentmods.dev/badge/skills/summarybotng/summarybot-ng/regression-testing/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for regression-testing

Your own site · 80×15
<a href="https://agentmods.dev/skills/summarybotng/summarybot-ng/regression-testing"><img src="https://agentmods.dev/badge/skills/summarybotng/summarybot-ng/regression-testing.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 41 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,567 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00041 $0.01567
Opus 5 $0.00020 $0.00783
Sonnet 5 $0.00008 $0.00313
Haiku 4.5 $0.00004 $0.00157

Measured 5d ago against content hash f040fdfa356c, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-09, from the pricing page.

Security

Grade A, and why

regression-testing scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 5d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

.claude/skills/regression-testing/SKILL.md · 234 lines

How it starts

The opening of the file, as written. The whole thing — 234 lines — stays where its author put it; the contents beside it link to each section on GitHub.

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
function selectTests(changedFiles: string[]): string[] {
  const testsToRun = new Set<string>();

  for (const file of changedFiles) {
    // Direct tests
    testsToRun.add(`${file.replace('.ts', '.test.ts')}`);

    // Dependent tests (via coverage mapping)
    const dependentTests = testCoverage[file] || [];
    dependentTests.forEach(t => testsToRun.add(t));
  }

  return Array.from(testsToRun);
}

// Example: payment.ts changed
// Runs: payment.test.ts, checkout.integration.test.ts, e2e/purchase.test.ts

Read the full file on GitHub · 234 lines

Files

What ships with it

3 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 5d ago First seen · 234 lines · 41 tokens per session scan A f040fdfa356c

Subscribe to this mod's changes

regression-testing is a skill published in the GitHub repository summarybotng/summarybot-ng (2 stars, last pushed 3mo ago), licensed MIT. It adds 41 tokens to every session and 1,567 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.

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