Validate your Cursor code in flow

Ship better software with Kerno + Cursor

Kerno writes, runs, and maintains integration tests right in your IDE – Instantly validate your Cursor backend changes against real dependencies in flow.
Try Kerno for free
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
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.

Focus
Automated backend integration testing
General AI coding assistant that can write tests
Test Generation
Automated
Detects endpoints, database schemas, and dependencies, then generates runnable integration tests automatically
Manual
Can generate test files through LLM completions, but requires explicit back and forth prompting
Test Execution
Built-in
Runs tests automatically in isolated environments with containers, seeded data, and teardown logic
External
No built-in execution layer; relies on user-managed test frameworks
Environment setup
Automated
Automatically provisions Postgres, Redis, or other dependencies through Docker Compose
Manual
Developer must configure all dependencies manually
Test maintenance
Automated
Tracks API, schema, and config changes, then self heals or adds/removes affected tests
Manual
No automatic maintenance; generated tests must be manually updated
Change Intelligence
Built-in
Compares baseline and head commits to identify regressions
None
No regression comparison or state tracking
Reliability
Built-in
Deterministic guardrails ensure tests always run successfully out of the box
None
Quality depends on prompt phrasing and LLM randomness
Try Kerno for free
Try Kerno for free
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 orchestrates your app and its dependencies locally and mocks external dependencies with zero manual setup or configuration.

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
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
FAQs

Frequently asked questions

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

How does Kerno compare to Cursor for testing?
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?
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Try Kerno for free
Try Kerno for free
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