MCPInstall

n8n:reproduce-bug

Reproduce a bug from a Linear ticket with a failing test. Expects the full ticket context (title, description, comments) to be provided as input.

Installs
240
Last 24h
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Trending rank
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Security
Not audited

Install

Works with every agent the skills CLI supports.

npx skills add https://github.com/n8n-io/n8n --skill n8n:reproduce-bug
  1. 01

    Install

    Run the command in your project. The CLI asks which agents to install for.

  2. 02

    Describe the task

    Ask your agent for something this skill covers. It loads n8n:reproduce-bug automatically when relevant.

  3. 03

    Review the result

    The agent follows the SKILL.md steps, scripts and references bundled with the skill.

SKILL.md

The instructions your agent reads when the skill is triggered.

Bug Reproduction Framework

Given a Linear ticket context ($ARGUMENTS), systematically reproduce the bug with a failing regression test.

Step 1: Parse Signals

Extract the following from the provided ticket context:

  • Error message / stack trace (if provided)
  • Reproduction steps (if provided)
  • Workflow JSON (if attached)
  • Affected area (node, execution engine, editor, API, config, etc.)
  • Version where it broke / last working version

Step 2: Route to Test Strategy

Based on the affected area, pick the test layer and pattern:

AreaTest LayerPatternKey Location
Node operationVitest unitNodeTestHarness + nockpackages/nodes-base/nodes/*/test/
Node credentialVitest unitvitest-mock-extendedpackages/nodes-base/nodes/*/test/
Trigger webhookVitest unitmock IHookFunctions + vi.mock GenericFunctionspackages/nodes-base/nodes/*/test/
Binary dataVitest unitNodeTestHarness assertBinaryDatapackages/core/nodes-testing/
Execution engineVitest integrationWorkflowRunner + DI containerpackages/cli/src/__tests__/
CLI / APIVitest integrationsetupTestServer + supertestpackages/cli/test/integration/
ConfigVitest unitGlobalConfig + Containerpackages/@n8n/config/src/configs/__tests__/
Editor UIVitestVue Test Utils + Piniapackages/frontend/editor-ui/src/**/__tests__/
E2E / CanvasPlaywrightTest containers + composablespackages/quality/testing/playwright/

Step 3: Locate Source Files

Find the source code for the affected area:

  1. Search for the node/service/component mentioned in the ticket
  2. Find the GenericFunctions file (common bug location for nodes)
  3. Check for existing test files in the same area
  4. Look at recent git history on affected files (git log --oneline -10 -- <path>)

Step 4: Trace the Code Path

Read the source code and trace the execution path that triggers the bug:

  • Follow the call chain from entry point to the failure
  • Identify the specific line(s) where the bug manifests
  • Note any error handling (or lack thereof) around the bug

Step 5: Form Hypothesis

State a clear, testable hypothesis:

  • "When [input/condition], the code does [wrong thing] because [root cause]"
  • Identify the exact line(s) that need to change
  • Predict what the test output will show

Step 6: Find Test Patterns

Look for existing tests in the same area:

  1. Check test/ directories near the affected code
  2. Identify which mock/setup patterns they use
  3. Use the same patterns for consistency
  4. If no tests exist, find the closest similar node/service tests as a template

Step 7: Write Failing Test

Write a regression test that:

  • Uses the patterns found in Step 6
  • Targets the specific hypothesis from Step 5
  • Includes a comment referencing the ticket ID
  • Asserts the CORRECT behavior (test will fail on current code)
  • Also includes a "happy path" test to prove the setup works

Complete the test safety gate in /AGENTS.md before you run the test:

  • Trace side effects from imports, constructors, hooks, and mocked branches
  • Keep filesystem access in a test-owned temporary directory
  • Set N8N_USER_FOLDER before importing modules that resolve it
  • When a mock changes a state check, inspect and isolate the branch that it activates

Step 8: Run and Score

Run the test from the package directory (e.g., cd packages/nodes-base && pnpm test <file>).

Classify the result:

ConfidenceCriteriaOutput
CONFIRMEDTest fails consistently, failure matches hypothesisReproduction Report
LIKELYTest fails but failure mode differs slightlyReport + caveat
UNCONFIRMEDCannot trigger the failureReport: what was tried
SKIPPEDHit a hard bailout triggerReport: why skipped
ALREADY_FIXEDBug no longer reproduces on current codeReport: when fixed

Step 9: Iterate or Bail

If UNCONFIRMED after first attempt:

  • Revisit hypothesis — re-read the code path
  • Try a different test approach or layer
  • Maximum 3 attempts before declaring UNCONFIRMED

Hard bailout triggers (stop immediately):

  • Requires real third-party API credentials
  • Race condition / timing-dependent
  • Requires specific cloud/enterprise infrastructure
  • Requires manual UI interaction that can't be scripted

Output: Reproduction Report

Present findings in this format:


Ticket: [ID] — [title] Confidence: [CONFIRMED | LIKELY | UNCONFIRMED | SKIPPED | ALREADY_FIXED]

Root Cause

[1-2 sentences explaining the bug mechanism]

Location

FileLinesIssue
path/to/file.tsXX-YYDescription of the problem

Failing Test

path/to/test/file.test.ts — X/Y tests fail:

  1. test name — [failure description]

Fix Hint

[Pseudocode or description of the fix approach]


Important

  • DO NOT fix the bug — only reproduce it with a failing test
  • Leave test files in place as evidence (don't commit unless asked)
  • Run tests from the package directory (e.g., pushd packages/nodes-base && pnpm test <file> && popd)
  • Always redirect build output: pnpm build > build.log 2>&1
  • DO NOT look at existing fix PRs — the goal is to reproduce from signals alone

FAQ

What does the n8n:reproduce-bug skill do?

Reproduce a bug from a Linear ticket with a failing test. Expects the full ticket context (title, description, comments) to be provided as input.

How do I install n8n:reproduce-bug?

Run npx skills add https://github.com/n8n-io/n8n --skill n8n:reproduce-bug in your project. The skills CLI detects the agents you use and copies the skill into the right folder. For Claude Code you can also place the skill folder at ~/.claude/skills/n8n:reproduce-bug/ (personal) or .claude/skills/n8n:reproduce-bug/ (project).

Which AI agents can use n8n:reproduce-bug?

Any agent that supports the open Agent Skills format (a folder with a SKILL.md file), including Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, Windsurf, Cline, OpenCode and more.

Is n8n:reproduce-bug safe to install?

No partner security audit is available yet. Skills can run commands and scripts, so read the SKILL.md and any bundled files before installing.

Who maintains n8n:reproduce-bug?

It is published by n8n-io in n8n-io/n8n. It has 240 recorded installs.

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