Repository and flow mapping
Indexes code and documentation, identifies routes, MCP tools, jobs, queue consumers, and dependencies, and builds a code-intelligence graph for test planning.
Kerno
Kerno is an AI-assisted runtime QA tool for backend apps, testing APIs, workers, queues, and MCP servers to catch regressions and security issues before merge.
Runtime QA for backend applications
Kerno is an AI-assisted runtime QA tool for backend applications. It writes and runs tests against a running application and its real dependencies, helping developers and coding agents find functional, security, contract, and edge-case issues before changes merge.
The workflow starts by indexing a repository and mapping entry points and critical user flows. Kerno records how the backend behaves, then re-runs affected flows when code changes and presents evidence about the step that failed. Tests can be maintained as intentional product behavior evolves, with results available to individual engineers and, on higher plans, team workflows and analytics.
Backend runtime testing capabilities
End-to-end runtime tests
Tests complete journeys across APIs and real databases, queues, services, and other running dependencies rather than relying only on mocks.
Change-impact verification
Traces a code change to the entry points and flows it affects, then reports the broken step with expected and actual behavior.
Functional and security checks
Checks request and response contracts, authentication and authorization, edge cases, error handling, resilience, and applicable OWASP API and Web Top 10 risks.
Async and MCP testing
Covers background workers and queues, including Celery, Kafka, RabbitMQ, SQS, Azure Service Bus, and Graphile Worker, as well as MCP server tools.
Persistent tests and CI
Stores tests in the repository, supports custom rules and evolving baselines, and provides a GitHub Action for pull-request validation with JUnit results.
Where Kerno fits in a backend workflow
Validating AI-assisted code changes
After an agent or developer changes routes, services, or persistence logic, Kerno identifies affected flows and reruns them against the live local stack before the pull request is merged.
Testing critical user journeys
Teams can model journeys such as signup, project creation, invitations, checkout, or refunds and check the complete sequence instead of validating endpoints in isolation.
Checking jobs and message-driven systems
Organizations running asynchronous systems can exercise real workers and queues, then inspect the database writes or messages produced by the consumer.
Verifying MCP servers and agents
Teams building tool-using applications can test MCP tools at runtime, including schemas, returned content, authentication behavior, and error handling.
Adding runtime checks to CI and team review
Teams can run the same repository-based tests locally and on pull requests, while the Portal provides coverage, run reports, drift, and repository-level views for team oversight.
Pros and Cons
Pros
- Exercises backend behavior against real databases, queues, services, and authentication flows rather than only mocks.
- Connects code changes to the user flows and entry points they affect, making regression checks more targeted.
- Includes runtime security checks covering applicable authorization, injection, data-exposure, SSRF, and related API risks.
- Keeps tests and custom rules in the repository and can run them in pull-request CI with deterministic JUnit output.
- Supports backend patterns beyond synchronous HTTP endpoints, including queues, background jobs, MCP servers, and AWS serverless configurations.
Cons
- The product is centered on validating a running backend and real dependencies, so it is not presented as a replacement for all unit, static-analysis, or code-review practices.
- The free Community plan is limited to 30 test runs per month, one repository, and one user.
- Some organizational capabilities, including SSO/SAML, self-hosting, audit logs, and dedicated support, are reserved for Enterprise.
FAQ
How do you get started with Kerno?
Install the CLI with `npm i @kerno/cli`, authenticate, and begin validating a running application. The Community plan does not require a credit card.
How does Kerno test a backend?
Kerno indexes the repository, identifies entry points and dependencies, connects to the running environment, and helps map critical flows. It then plans and runs tests against real services, records a baseline, and re-runs affected flows after code changes.
What kinds of checks does Kerno perform?
Kerno can test end-to-end user flows across APIs, HTTP routes, MCP tools, background jobs, and queue consumers. It can also check contracts, authorization, OWASP API and Web Top 10 categories, edge cases, error handling, resilience, and AI-agent tool interactions.
What happens to test results and test maintenance?
Tests are saved in the repository as a baseline. Kerno can update entry-point tests and regenerate flows when behavior changes intentionally. Its GitHub Action can rerun tests on pull requests and return deterministic results in JUnit format.
Which plans are available?
The Community plan includes 30 test runs per month, one repository, one user, and custom context and rules. Pro adds unlimited runs, repositories, and users, plus team analytics and CI integration. Enterprise adds options including SSO/SAML, self-hosting, audit logs, data controls, and dedicated support with an SLA.
Quick Facts
- Category
- Developer tool
- Primary users
- Backend developers, engineering teams, and coding agents
- Core workflow
- Map, test, verify, and evolve backend flows
- Execution model
- Tests a running app against real dependencies
- CI integration
- GitHub Action with JUnit results
- Community plan
- $0 per developer per month; 30 test runs, 1 repository, and 1 user
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