Catch breaking backend changes before raising a PR

Kerno writes, runs, and maintains integration tests right in your IDE – Instantly validate your AI backend changes against real dependencies in flow.
Try Kerno for free
Try Kerno for free
1-click ● 5min install | No credit card required
Cursor
payment_service.py
[Cursor] Generating...
[Kerno] Starting Payments service and its dependencies ...
[Kerno] validating code changes ...
[Kerno] Validation completed (3s)
TEST ENVIRONMENT
docker-compose.yaml new Read Only
Kerno.md new Editable
Running services
Service under test (SUT) Port: 3000
Postgres v.16 Port: 5432
Redis v.7 Port: 6379
Stripe mock Port: 4242
1 diff detected
One or more behaviors for the POST /api/payment/status endpoint no longer match the baseline.
Result
Behavior
Diff
Payment status with valid ID returns response with...
Unchanged
Missing payment_id parameter returns 400 error w...
Unchanged
Payment API request includes correct headers and...
Unchanged
Payment status with completed state returns success response with amount, currency, and timestamp...
Unchanged
Payment status with pending state returns response indicating processing status...
Unchanged
Payment status response includes payment method, transaction ID, and merchant details...
Diff Report - Payment Status Endpoint
RESPONSE BODY
EXPECTED
{
      "detail": "Payment not found",
      "code": "PAYMENT_NOT_FOUND",
      "timestamp": "2025-11-21T10:20:56.000Z",
      "request_id": "req-abc-123",
      "data": null
    }
ACTUAL
{
      "detail": "Payment not found",
      "code": "PAYMENT_NOT_FOUND",
      "status": 404,
      "error": true,
      "timestamp": "2025-11-21T10:20:56.000Z",
      "request_id": "req-abc-123",
      "data": null,
      "metadata": { ... }
    }
Trusted by AI-native backend teams
AI-native feedback loops

Instant, 1-click validation for every AI-generated code changes

Automated Env Setup
Diff Detection & Validation
Self-Healing & Maintenance

Kerno automatically spins up your app and its dependencies locally and mocks external dependencies with zero manual setup or configuration.

Supported supported envs  →

"Kerno was up and running in minutes with no manual work, and it made our API migration so much smoother. We could instantly validate that every change made by Cursor worked the way we expected, and now it's a core part of our how we build."

Misch Strotz
Co-Founder & CEO
Supports your dependencies

Kerno captures the baseline behavior of critical paths for your REST endpoints, then compares your code changes to the baseline and flags diffs.

Learn about diff detection →
Kerno will validate:

As your app evolves, Kerno updates your baseline tests to keep everything in sync without manual effort.

Learn about test maintenance →

"Kerno saves us a lot of manual work and helps us catch side effects and issues that would definitely break our projects' backends. Our engineering team loves it."

Santiago J. Valls
Co-Founder & CTO

Ship better software 
with Kerno +

Integrates with your IDE

"Using Kerno with Claude Code has been a game changer. You get quick feedback with no manual effort, and it saves you a lot time and hassle debugging integration issues post-merge."

Jonathan Bernales
CTO
35%

Fewer breaking backend changes and unintended side effects.

3X

faster feedback loops for developers, leading to fewer PR bottlenecks

10h+

Saved each week per developer troubleshooting integration issues post CI.

Full cobebase context

Kerno indexes your codebase to build a deep understanding of how everything works together and test every critical flow  of your application.

Supports your backend language
Coming soon
Your code is always secure

Safe, secure, and private by design

Kerno is currently undergoing a Service Organization Controls audit (SOC 2 Type II).
Kerno encrypts data in-transit with TLS 1.2 and at-rest using AES 256-bit encryption.
Your private code is strictly off-limits and is never stored or used for training purposes.
Pricing

Simple, transparent pricing

Billed annually
Billed monthly
YOUR CURRENT PROCESS

$900/ Dev / Month*

Before Kerno
PRO

$19/ Dev/Month

Try Kerno for free
Try Kerno for free
YOUR CURRENT PROCESS

$900/ Dev / Month*

Before Kerno
PRO

$25/ Dev/Month

Try Kerno for free
Try Kerno for free
FAQs

Frequently asked questions

Got more questions? Drop us a message in our community Slack — we’re happy to help.

What is Kerno?
What makes Kerno different from other tools?
Does Kerno support my programming language?
Does Kerno store my code?
Does Kerno use my code for training LLMs?
Are there discounts available for startups?
TRY KERNO NOW
Try Kerno for free
Try Kerno for free
Install in 5 mins | No credit card required
© 2025 FYCK Limited. All Rights Reserved
AboutDocsCareersBlogContact UsKerno Vs Cursor
Terms of ServicePrivacy Policy