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Content Negotiation

Some APIs might use content negotiation versioning which implies formats like application/v11+json in the Accept header.

You can handle this in CATS as follows:

  • if the OpenAPI contract defines its content as:
 requestBody:
        required: true
        content:
          application/v5+json:
            schema:
              $ref: '#/components/RequestV5'
          application/v6+json:
            schema:
              $ref: '#/components/RequestV6'

by having clear separation between versions, you can pass the --contentType argument with the version you want to test: cats ... --contentType="application/v6+json".

If the OpenAPI contract is not version aware (you already exported it specific to a version) and the content looks as:

 requestBody:
        required: true
        content:
          application/json:
            schema:
              $ref: '#/components/RequestV5'

and you still need to pass the application/v5+json Accept header, you can use the --headers file to add it:

all:
  Accept: "application/v5+json"

Supported payload formats and Accept negotiation​

By default, CATS supports request bodies declared with:

  • application/json and *+json media types
  • application/x-www-form-urlencoded
  • text/plain
  • application/x-ndjson and application/ndjson

For Accept headers, CATS automatically negotiates a media type declared under the operation's 2XX responses in the OpenAPI contract when present, falling back to the default content type (application/json) otherwise.