FlakeMonster

Surface flaky tests by injecting deterministic async delays

░  Your test ran too fast and left a bug behind.

░  Your test flaked!

In your development environment:

That's why your tests are flaking.

Inject await delays between statements to surface bugs.

$ npx flake-monster test --cmd "npm test"
$ npm install flake-monster
<script type="module" src="https://unpkg.com/flake-monster@0.4.6">
$ curl -L registry.npmjs.org/flake-monster/-/flake-monster-0.4.6.tgz | tar xz
npm · GitHub · v0.4.6
Real demos! No mocks!

How It Works

FlakeMonster uses Acorn to parse your code into an AST, walks the tree to find async functions and top-level module statements, injects delay nodes, then generates the modified source.

→ → → → →
Your JavaScript source code.

Operational Jitter

See how FlakeMonster reorders async operations by injecting deterministic delays.

Without FlakeMonster

With FlakeMonster

Code Injection Intensity

Watch FlakeMonster inject delay statements into real JavaScript code.

Original

Injected

File / Seed Based Determinism

Each seed is combined with the file path and function name to derive a unique delay. Same seed, same delays, every run.

seed
src/user.jsloadUser()
src/cart.jsgetCart()
lib/auth.jscheckAuth()

  


  
  

    

      
Agent Skill

      
Uses the open Agent Skills standard. One SKILL.md works across Claude Code, Codex, Copilot, and more.

    


    

      

        

          

            
              
              
            
          

          

            Install the skill
            One command drops the skill file into your project
          

        

        

          
        

        

          

            
              
              
            
          

          

            Use the slash command
            Type /flakemonster followed by your test command
          

        

        

          
        

        

          

            
              
            
          

          

            Get a flake report
            Your agent runs multiple seeds, analyzes results, and reports flaky tests
          

        

      


      

        

          

            
            
            
            
            
            
          

          

            
$ mkdir -p .claude/commands && \
  curl -sL https://raw.githubusercontent.com/growthboot/FlakeMonster/refs/heads/main/SKILL.md \
  -o .claude/commands/flakemonster.md

            
$ mkdir -p .cursor/skills/flakemonster && \
  curl -sL https://raw.githubusercontent.com/growthboot/FlakeMonster/refs/heads/main/SKILL.md \
  -o .cursor/skills/flakemonster/SKILL.md

            
$ mkdir -p .agents/skills/flakemonster && \
  curl -sL https://raw.githubusercontent.com/growthboot/FlakeMonster/refs/heads/main/SKILL.md \
  -o .agents/skills/flakemonster/SKILL.md

            
$ mkdir -p .github/skills/flakemonster && \
  curl -sL https://raw.githubusercontent.com/growthboot/FlakeMonster/refs/heads/main/SKILL.md \
  -o .github/skills/flakemonster/SKILL.md

            
$ mkdir -p .windsurf/skills/flakemonster && \
  curl -sL https://raw.githubusercontent.com/growthboot/FlakeMonster/refs/heads/main/SKILL.md \
  -o .windsurf/skills/flakemonster/SKILL.md

            
$ mkdir -p .agent/skills/flakemonster && \
  curl -sL https://raw.githubusercontent.com/growthboot/FlakeMonster/refs/heads/main/SKILL.md \
  -o .agent/skills/flakemonster/SKILL.md

          

        


        

          

            
            Usage
          

          
// Type in any supported agent:
/flakemonster npm test
/flakemonster npx playwright test
/flakemonster --runs 20 --mode hardcore npx jest

        

      

    

  


  
  

    

      New
      
FlakeMonster CI

      
Catch flaky tests on every pull request. Automatically.

    


    

      
      

        

          

            

              
                
                
              
            

            

              Add one file
              Drop a YAML workflow into your repo
            

          

          

            
          

          

            

              
                
                
              
            

            

              Push code
              FlakeMonster runs 5 seeds on every PR
            

          

          

            
          

          

            

              
                
              
            

            

              See results
              A detailed comment lands on your PR
            

          

        


        

          

            
            .github/workflows/flake-monster.yml
          

          
name: FlakeMonster
on: [pull_request]

jobs:
  flake-check:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: actions/setup-node@v4
      - run: npm ci
      - uses: growthboot/FlakeMonster-Action@v1
        with:
          test-command: npm test
          runs: 5

        

      


      
      

        

          

            

              
            

            

              flake-monster bot 2 min ago
            

          

          

            

              
              Found 2 flaky tests across 5 seeds
            

            

              
                

                  
                  Test
                  Result
                  Failed seeds
                

              
              
                

                  
                  checkout › applies discount
                  3/5
                  17 42
                

                

                  
                  auth › refresh expired token
                  4/5
                  89
                

                

                  
                  cart › adds item
                  5/5
                  , 
                

                

                  
                  user › loads profile
                  5/5
                  , 
                

              
            

            

              Seeds: 7 17 42 63 89
              
                
                FlakeMonster
              
            

          

        

      

    

  


  
  

    

      
Pricing

      
The CLI is free forever. The CI product adds automation and insights for teams that ship fast.

    


    

      

        

          
            
            
            
            
            
            
            
          
        

        

          
Open Source

          
$0

          forever
        

        
Full CLI with inject, test, and restore. Run locally, run in CI, run anywhere.

        
    
          
  • Full CLI & GitHub Action
    • 
          
  • 50 CI checks per month
    • 
          
  • PR comments with results
    • 
          
  • Community support
    • 
        

        
          
          Get started
        
      

      

        

          
            
            
            
            
            
            
            
            
          
        

        

          
Team

          
$29/mo

          per team
        

        
For teams that need visibility across every repo. Track trends, get alerted, and stop flaky tests before they spread.

        
    
          
  • Unlimited CI checks
    • 
          
  • Priority support
    • 
          
  • Everything in Free
    • 
          
  • Cancel anytime
    • 
        

        Get started
      

    

  


  
  

    

      
Planned Features

      
FlakeMonster is just getting started. Here's what's coming next.

    


    

      

        

          
            
            
            TS
            PY
          
        

        Up next
        
More language support

        
TypeScript, Python, Go, and beyond. The adapter architecture is ready — new languages just need a parser and codegen layer.

      


      

        

          
            
            
            
            
            
          
        

        Planned
        
CI dashboard

        
A web dashboard to track flaky test trends across repos and seeds over time. See which tests are getting worse before they break.

      


      

        

          
            
            
            
            
            
            
            
          
        

        Planned
        
IDE integration

        
VS Code extension to inject and restore delays without leaving your editor. One-click flake testing from your sidebar.

      


      

        

          
            
            
            
            
          
        

        Planned
        
Monorepo support

        
First-class workspace support for monorepos. Run FlakeMonster across packages with shared seeds and unified reporting.

      


      

        

          
            
            
          
        

        Exploring
        
Timing profiles

        
Named delay profiles (network, database, filesystem) that model real-world latency patterns instead of uniform random delays.

      


      

        

          
            
            
          
        

        
Your idea here

        
Have a feature request or found a bug? We'd love to hear from you.

        
          
          Open an issue on GitHub