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examples

Email testing and SMS verification examples using MailSlurp and a wide range of frameworks.

n8n Email OTP Verification Test

This project demonstrates OTP email verification testing using n8n workflow automation and the MailSlurp API. The workflow creates a real email inbox, signs up on a test site, waits for a verification email, extracts the OTP code, and completes the verification process.

Overview

n8n is a free, open-source workflow automation tool that can self-host or run locally. This example shows how to test email-based OTP verification flows using n8n’s visual workflow editor and MailSlurp’s disposable email addresses.

Workflow Steps

  1. Create Inbox - HTTP Request to MailSlurp API creates a real email address
  2. Browser Signup - Execute Command node runs Puppeteer script to fill signup form
  3. Wait for Email - HTTP Request polls MailSlurp API for verification email
  4. Extract OTP - Code node uses regex to extract 6-digit verification code
  5. Submit OTP - Execute Command node runs Puppeteer to enter code
  6. Verify Login - Check for “Welcome” message confirming successful verification
  7. Return Result - Output success status with email address and verification confirmation

Prerequisites

Installation

# Install dependencies
make install

# Start n8n
make start

# Run test (in separate terminal)
make test

# Clean up
make clean

Manual Setup

# Install dependencies
npm install

# Start n8n
npm start
# or
npx n8n start

# Access UI
open http://localhost:5678

Configuration

Set API Key

Option 1: Environment Variable

export MAILSLURP_API_KEY=your_api_key_here
make start

Option 2: n8n Credentials

  1. Open n8n UI at http://localhost:5678
  2. Click “Credentials” in the left sidebar
  3. Add “HTTP Header Auth” credential:
    • Name: MailSlurp API Key
    • Header Name: x-api-key
    • Header Value: your_api_key_here

Import Workflow

Option 1: Auto-import (via Makefile)

make import-workflow

Option 2: Manual Import

  1. Start n8n: npm start
  2. Open http://localhost:5678
  3. Click “Import from File”
  4. Select workflows/otp-verification-workflow.json

Running the Workflow

Via n8n UI

  1. Open the imported workflow
  2. Click “Execute Workflow” button
  3. Watch nodes execute in sequence
  4. Check execution log for results

Via Test Script

# Run standalone test
make test

# Or directly
node test/otp-verification-test.js

Via API

# Trigger workflow via webhook
curl -X POST http://localhost:5678/webhook/otp-test

Project Structure

n8n-email-otp-test/
├── README.md                          # This file
├── package.json                       # Dependencies
├── Makefile                           # Build automation
├── .env.example                       # Environment variable template
├── workflows/
│   └── otp-verification-workflow.json # n8n workflow definition
├── scripts/
│   ├── browser-signup.js              # Puppeteer signup script
│   ├── browser-verify.js              # Puppeteer OTP submission script
│   └── extract-otp.js                 # OTP extraction logic
└── test/
    └── otp-verification-test.js       # Standalone test runner

Workflow Nodes

1. Start Node

Triggers the workflow manually or via webhook.

2. Create Inbox (HTTP Request)

POST https://api.mailslurp.com/inboxes
x-api-key: 
Content-Type: application/json

Outputs:

3. Browser Signup (Execute Command)

node scripts/browser-signup.js

Opens Chrome via Puppeteer, navigates to https://playground.mailslurp.com, fills signup form.

4. Wait for Email (HTTP Request)

GET https://api.mailslurp.com/waitForLatestEmail
  ?inboxId=
  &timeout=60000
  &unreadOnly=true
x-api-key:

Polls with 60-second timeout until email arrives.

5. Extract OTP (Code Node)

const emailBody = $input.item.json.body;
const match = emailBody.match(/([0-9]{6})$/m);
return [{
  json: {
    otpCode: match ? match[1] : null,
    emailSubject: $input.item.json.subject,
    emailBody: emailBody
  }
}];

Uses regex to extract 6-digit code from email body.

6. Submit OTP (Execute Command)

node scripts/browser-verify.js \\
   \\

Enters OTP code, logs in, verifies “Welcome” message.

7. Return Result (Set Node)

{
  "success": true,
  "message": "OTP Email Verification Completed",
  "details": {
    "emailAddress": "",
    "inboxId": "",
    "otpCode": "",
    "verified": true
  }
}

Troubleshooting

n8n Won’t Start

Error: Port 5678 already in use

Solution:

# Kill existing n8n process
pkill -f n8n

# Or use different port
n8n start --port 5679

API Key Not Working

Error: 401 Unauthorized

Solution:

  1. Check API key is correct: https://app.mailslurp.com/settings
  2. Verify key is set in environment or n8n credentials
  3. Check key has no extra spaces/quotes

Chrome Not Found

Error: Puppeteer can’t find Chrome executable

Solution:

# macOS
export PUPPETEER_EXECUTABLE_PATH="/Applications/Google Chrome.app/Contents/MacOS/Google Chrome"

# Linux
export PUPPETEER_EXECUTABLE_PATH="/usr/bin/google-chrome"

# Or install Chromium via Puppeteer
npx puppeteer browsers install chrome

Email Not Received

Error: Timeout waiting for email

Solutions:

  1. Increase timeout in “Wait for Email” node (default 60000ms)
  2. Check inbox ID is correct
  3. Verify email was actually sent (check playground site)
  4. Try manual API call: 
    curl "https://api.mailslurp.com/waitForLatestEmail?inboxId=YOUR_INBOX_ID&timeout=60000" \\
  -H "x-api-key: YOUR_API_KEY"

OTP Not Extracted

Error: OTP code is null

Solutions:

  1. Print email body in Code node to inspect format
  2. Adjust regex pattern for your email format:
    • End of line: /([0-9]{6})$/m
    • After “code:”: /code:\s*([0-9]{6})/
    • Any 6 digits: /([0-9]{6})/
  3. Check email body field (not htmlBody)

Advanced Usage

Custom Webhook Trigger

Modify Start node to use Webhook trigger:

  1. Replace Start node with Webhook node
  2. Set path: /webhook/otp-test
  3. Set method: POST
  4. Trigger via HTTP: 
    curl -X POST http://localhost:5678/webhook/otp-test

Scheduled Execution

Add Schedule Trigger node:

  1. Click “+” to add node
  2. Select “Schedule Trigger”
  3. Set interval (e.g., every 1 hour)
  4. Connect to workflow

Email Notifications

Add Email Send node at end:

  1. Click “+” after Return Result
  2. Select “Email Send (SMTP)” or “Gmail” node
  3. Configure SMTP settings
  4. Send summary email on completion

Documentation