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openapi-verifier

Introduction

Verifies API responses against an OpenAPI specification. A response body that does not match its documented schema is reported as a mismatch, so the specification and the API cannot drift apart unnoticed.

Supported ways to hook in:

• Laravel and Slim tests: a trait for the framework's test case. Every response a test receives is verified.
• PSR-15 middleware: verifies the responses of any PSR-15 stack, such as Slim or Mezzio.
• Guzzle and PSR-18 clients: verifies responses on the client side, against a running server or a mock.
• The verifier on its own: OpenApiVerifier needs only a request and its response.

Requirements

• PHP 8.2 or higher

Installation

You can use composer or simply download the release.

Composer

The preferred method is via composer. Follow the installation instructions if you do not already have composer installed.

Once composer is installed, execute the following command in your project root to install this library:

After that all required classes should be available in your project.

Some features need further packages, such as a framework adapter or YAML support. They are listed as suggestions, and composer suggests radebatz/openapi-verifier shows them.

Usage

The verifier

OpenApiVerifier checks a response against the specification. It needs no test case and no framework, so anything that sees a request and its response can use it.

The specification can be a JSON or YAML file, or an already decoded object.

How the response is looked up:

• Path: a literal match first, then the path templates, so /user/1 finds /user/{id}. When several templates match, the one with the most literal characters wins. A base path from servers is stripped first, and the optional third argument of verify() skips the matching and uses the given template.
• Status code: the exact code, then its range (2XX), then default.
• Media type: the response's Content-Type, including +json types such as application/problem+json. Without a match it falls back to application/json, so a JSON body labelled text/html is still validated.

Bodies are validated with opis/json-schema, which supports JSON Schema 2020-12, the dialect of OpenAPI 3.1. OpenAPI 3.0 documents are translated first: nullable and the boolean form of exclusiveMinimum and exclusiveMaximum become their 2020-12 equivalents.

Another engine can be used by passing a Schema\SchemaValidator to the verifier. It gets each schema as the document writes it, together with the document's OpenAPI version, so it can handle 3.0 its own way or use Schema\OpenApi30Translator.

A mismatch carries one Schema\SchemaError per problem, with a JSON pointer into the body, the failing keyword and a message. getErrorSummary() groups them:

What is verified

Only response bodies are verified. Requests, parameters and response headers are not checked.

A response is only verified if the specification has a schema for it. A path, method or status code without one is skipped: verify() returns false and the adapters do nothing.

The body is validated against that schema as written:

• required properties and types are checked.
• Formats that opis knows, such as date-time and email, are checked.
• Properties the schema does not declare are allowed, unless it sets additionalProperties: false.
• A body that is not valid JSON is validated as null, so it fails. With a Content-Type that is not JSON it is skipped instead.

Guzzle and PSR-18 clients

Verifying on the client side needs no framework. It works against a running server, a mock handler or anything else a client can talk to.

Guzzle: push the middleware onto the handler stack. A response that does not match makes the request throw OpenApiSchemaMismatchException.

PSR-18: wrap any Psr\Http\Client\ClientInterface, Guzzle's included.

Either way the response body is left at its start, so it can be read as usual afterwards.

Manual verification

The VerifiesOpenApi trait can be used directly and customized in 3 ways in order to provide the reqired OpenApi specifications:

• Overriding the method getOpenApiSpecificationLoader() as shown below
• Populating the $openapiSpecificationLoader property.
• Setting a property $openapiSpecification pointing to the specification file

PSR-15 middleware

Any PSR-15 stack (Slim, Mezzio and others) can verify its responses with the middleware. A response that does not match throws OpenApiSchemaMismatchException. An optional callback is called with the exception and the response first, to report the mismatch in a way of your own.

Laravel adapter

The adapter will try to resolve the specification dynamically in this order:

• filename passed into registerOpenApiVerifier()
• /tests/openapi.json
• /tests/openapi.yaml
• Generate specification from scratch by scanning the app folder

The code expects to be in the context of a Laravel Test\TestCase.

Slim adapter

The adapter will try to resolve the specification dynamically in this order:

• filename passed into registerOpenApiVerifier()
• /tests/openapi.json
• /tests/openapi.yaml
• Generate specification from scratch by scanning the src folder

Simplest way is to register the verifier in the Tests\Functional\BaseTestCase.

The adapter adds the PSR-15 middleware below, and a mismatch fails the test with the error summary and the response body.

Upgrading from 2.x

Requirements

• PHP 8.2 or higher.
• opis/json-schema replaces justinrainbow/json-schema.
• symfony/psr-http-message-bridge 7 is allowed alongside 6.

Validation

• A $ref must be a JSON pointer such as #/components/schemas/User. justinrainbow also accepted #components/schemas/User, which now fails as an unresolved reference.
• Messages are opis's: "The required properties (name) are missing" where it was "The property name is required".
• OpenAPI 3.1 documents are no longer rewritten. A nullable in one has no effect, as in the specification.

API

• OpenApiSchemaMismatchException::getErrors() returns Schema\SchemaError objects.
• OpenApiSpecificationLoader::getResponseSchemaUrlFor() and findPath() are removed. getResponseSchemaFor() returns the schema with its components attached.
• VerifiesOpenApi::verifyOpenApi() takes a RequestInterface.
• VerifiesOpenApi::failSchemaMismatch() returns void and joins its parts with newlines.
• $openapiSpecification is object|string|null, with a null default.

Adapters

• Nothing is put in a container any more, and OPENAPI_VERFIER_CONTAINER_KEY is gone from both middleware.
• Adapters\Slim\OpenApiVerifierMiddleware and Adapters\PSR17Middleware are removed. The PSR-15 middleware replaces the first.
• The Slim adapter's registerOpenApiVerifier() requires an App.
• The Laravel middleware is final and takes an OpenApiVerifier in its constructor.
• The Slim verifier can be registered before or after the routing middleware.

License

The openapi-verifier project is released under the MIT license.