API Test Generator
Auto-generate tests for your API endpoints and responses
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How many of your endpoints have a test that checks what happens on a bad request? Do you test the happy path and hope the rest holds? API Test Generator writes the test suite for an endpoint you describe, including the responses that only appear when something goes wrong.
Short answer: API Test Generator writes a test suite for an endpoint you describe, covering status codes, response shapes, validation failures and authentication paths, written in the language and test framework your project already uses.
What is API Test Generator?
API Test Generator is a free tool that produces API tests from a description. You say what the endpoint does, what it accepts and what it returns, and the output is a set of tests: the successful case, the validation failures, the unauthorised request, and the assertions that check the response body rather than only the status code.
Language, API Style And Auth
| Option | What it controls | Where to start |
|---|---|---|
| Language / Framework | The stack the tests are written for, such as FastAPI or Laravel | Name yours, or leave it on Auto and say it in the description |
| API Style | REST, GraphQL, RPC, CRUD, webhook or microservice | REST for a conventional resource endpoint |
| Output | Endpoint code, full route, code with docs, code with tests, spec or schema | Code + Tests, which is what produces the suite |
| Auth | API key, JWT, OAuth, session or basic | Whatever the endpoint really uses, so the tests exercise it |
Include Validation and Include Error Handling are the toggles that change the suite most, since they are what pull the failure cases into the output. Include Docs adds explanatory comments, useful when the tests double as documentation for a new joiner.
What The Generated Suite Covers
Status and body
Assertions on the response shape and fields, not just on a 200 coming back.
Validation failures
Missing fields, wrong types and out of range values, each with the expected response.
Auth paths
Missing credentials, expired tokens and the wrong user, which is where real bugs hide.
How Does API Test Generator Work?
- Describe the endpoint: resource, methods, fields, and what it returns.
- Pick a model, then set Language / Framework, API Style and Auth.
- Set Output to Code + Tests, then generate.
- Copy the suite into your project and run it against a real server.
Describing An Endpoint Precisely
Give the method and path, every field with its type and whether it is required, the success response, and the error responses you have defined. If a field has a rule, such as a maximum length or a value that must exist in another table, say so. Those rules become the tests that catch regressions, and they are exactly what a description written in a hurry leaves out.
Reading The Tests Before You Trust Them
Important A generated suite that passes immediately is suspicious. Check that the assertions test real values from your API rather than placeholders, and confirm each failure case actually fails without your fix in place.
Then look at what is missing. The tests describe the endpoint you described, so any behaviour you forgot to mention is untested and looks covered. When a test fails for a reason you cannot place, paste the failure into the Error Fixer before assuming the code is wrong.
Testing tools on EizTools cost nothing to open, with no registration and no ceiling on how often you run them, and the model selector lets you regenerate the suite through a different engine when the assertions come back shallow. API Test Generator sits with the testing tools in the coding tools category, alongside the other test writing tools.
Frequently Asked Questions
Can it work from an OpenAPI spec?
Yes. Paste the relevant part of the spec instead of writing a description, and the tests follow the documented fields, status codes and error responses.
Does it handle GraphQL?
Set API Style to GraphQL and describe the query or mutation with its variables. The tests then assert on the data and errors structure rather than on status codes alone.
Will the tests run without changes?
Usually they need your base URL, fixtures and auth setup wiring in. The test bodies are the time saving part, not the project scaffolding around them.
How do I test rate limiting or timeouts?
Describe the behaviour explicitly in the prompt. Anything the description omits will not appear, and rate limits are the most commonly forgotten case.
API tests are written when there is time and skipped when there is not, which is precisely backwards. Producing the first suite from a description costs a minute, and it makes the failure cases visible while the endpoint is still fresh in your head.
Sabir Bepari
Founder of EizTools and a passionate AI enthusiast dedicated to building practical, user-friendly AI tools that simplify everyday tasks.
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