Continuous testing for every API endpoint, against your real stack.
Kerno writes, runs and maintains tests for every endpoint, catching functional, security and behavior issues before you open a pull request.
Faster merges, with every endpoint tested against your real stack.
6×
Faster merges for PRs tested by Kerno
72%
Of planted runtime bugs caught across real open-source backends
11 of 14
Critical-severity bugs caught across 7 open-source backends
11 of 14
State bugs caught, from dropped fields to dead reset links
Agents and engineers at these companies use Kerno
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 how we build.
Misch StrotzCo-Founder & CEOUsing Kerno with Claude Code has been a game changer. You get quick feedback with no manual effort, and it saves you a lot of time and hassle debugging integration issues post-merge.
Jonathan BernalesCTOKerno 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. VallsCo-Founder & CTORegressions have always been a huge bottleneck for our team. Kerno has been a force multiplier helping us ship releases much faster without the manual overhead of QA.
Ronan HigginsCTODeep code analysis keeps every API test accurate as your codebase changes.
Finds every endpoint your codebase exposes
A compiler-grade index and call graph, so routes your framework generates are found alongside the ones you wrote.
Plans each test from what the endpoint calls
Every dependency, side effect and auth guard on the path is read from the call graph and covered.
Re-tests only what a change actually affects
Kerno maps the blast radius of a change through the call graph and re-runs the endpoints inside it.
Checks the state each request leaves behind
The database rows it wrote, the messages it queued and the downstream services it called, alongside the response.
Gates every run so a failure is a real failure
Pre-flight checks confirm the environment is ready, and every scenario passes an adversarial review before it runs.
Flags every behavior change on the next run
A baseline records how your API behaves today, and the following run reports each field that moved.
Covers behavior, contracts, authorization and edge cases across your backend.
Functional workflows
Endpoint behavior, multi-step sequences, and coordinated service interactions.
Contract & schema
Request and response structures, data types, required fields, and version compatibility.
Authorization
Token validation, role-based access, permission scopes, and session handling.
Error handling
Status codes, error bodies, retries, timeouts, and fallbacks.
Boundary & edge cases
Payload limits, pagination, null and empty values, malformed input, and unexpected types.
Security
OWASP API and Web Top 10 on demand, including BOLA, injection, SSRF, and mass assignment.
TypeScript
JavaScript
Python
Java
Kotlin
Go
Ruby
PHP
C#
Rust
C
PostgreSQL
MySQL
MariaDB
MongoDB
Redis
Kafka
RabbitMQ
AWS
Azure
ClickHouse
Google Cloud
Kerno applies your rules and standards to every test it writes and runs.
Reads your rules and standards in plain English
Write a rule the way you would explain it to a new engineer, and scope it to the repositories and paths it applies to.
Works from the context your team already wrote
Agent instruction files, service READMEs and the docs in your repository shape how every test gets planned.
Gets more accurate with every run you review
Kerno learns from each run and the feedback you give it, and carries what it learns into the tests that follow.
01How does Kerno test REST APIs?
Kerno reads your routes and handlers, builds a scenario per endpoint, and runs each against your live services. Every scenario checks the response and the side effects, and the suite replays in CI on every change.
02Does Kerno need my OpenAPI spec?
No. Kerno reads your routes and handlers directly from the code, so it works whether or not you maintain an OpenAPI spec.
03Can Kerno test authenticated endpoints?
Yes. Kerno mints real credentials and tests token validation, role-based access, and permission scopes across your endpoints.
04Does Kerno do black-box or white-box API testing?
Both. With database access Kerno seeds and verifies state directly; over HTTP alone it tests black-box, and it blocks any scenario the environment cannot satisfy up front.
05Which languages and frameworks does Kerno support?
Kerno reads every major backend language, from TypeScript and Python to Go, Rust, Ruby, PHP, C#, Java, Kotlin, and Scala, and resolves each framework's own routing on top of that.
06Does Kerno run API tests in CI?
Yes. Committed scenarios replay in CI on every pull request, and a behavior change fails the check.