API Auto Mocking

If an operation has multiple response codes, the mock returns the response with the lowest status code. For example, if an operation has responses 201, 202 and 400, the mock returns the 201 response.

When using OpenAPI 3.0 wildcard response ranges, such as 4XX, the lowest code of that range is returned – in this example, 400.

If an operation defines just the default response instead of specific status codes, the mock returns status 200 for GET, HEAD, DELETE and OPTIONS, and status 201 for POST, PUT and PATCH.

Requests to non-existent paths return HTTP status 404 "Not Found".

Requests that use HTTP methods not defined for the given path will return HTTP status 405 "Method Not Allowed" (except for OPTIONS, which always returns 200 to support CORS).

The response body is included if a schema is defined for the response. Mock responses use the example, default and enum values where possible. If your schemas do not include example values, the mock will generate values based on data types (integer, string, array and so on).

For example, this schema:

definitions:
  User:
    type: object
    properties:
      id:
        type: integer
        example: 42
      name:
        type: string
        example: Arthur Dent
    xml:
      name: user

will produce the following response for application/json:

{
  "id": 42,
  "name": "Arthur Dent"
}

for application/xml:

<?xml version='1.1' encoding='UTF-8'?>
<user>
  <id>42</id>
  <name>Arthur Dent</name>
</user>

for application/yaml:

---
id: 42
name: "Arthur Dent"

Alternatively, if media type examples are defined for the response, the mock will use those examples:

      # OpenAPI 2.0
      produces:
        - application/json
      responses:
        200:
          description: OK
          schema:
            type: object
          examples:
            application/json:
              id: 42
              name: Arthur Dent

In OpenAPI 3.0 definitions, if examples contain multiple examples, the first example will be used, except if it is an externalValue example, in which case the first non-external example will be used.

      responses:
        '200':
          description: OK
          content:
            application/json:
              schema:
                type: object
              examples:
                # This example will be used
                cat:
                  summary: An example of a cat
                  value:
                    name: Moon
                    petType: cat
                    color: gray
                    gender: female
                dog:
                  summary: An example of a dog
                  value:
                    name: Gromit
                    petType: dog
                    color: white
                    gender: male

To learn more about how to define API responses and examples, see the syntax guide on swagger.io:

OPTIONS requests are accepted on any paths (even non-existing ones) and with any headers, and always return 200 OK. This is done to avoid leaking of private API information through the mock and to support CORS. Custom handling of the OPTIONS method (returning custom status code and headers) is not supported.

Responses to OPTIONS requests include the following headers:

Access-Control-Allow-Origin: *
Access-Control-Allow-Methods: *
Access-Control-Allow-Headers: X-Requested-With,Content-Type,Accept,Origin

In CORS preflight requests, the response headers Access-Control-Allow-Headers and Access-Control-Allow-Methods mirror the corresponding request headers Access-Control-Request-Method and Access-Control-Request-Headers. For example, if a client sends:

OPTIONS /foo/bar HTTP/1.1
Access-Control-Request-Method: POST
Access-Control-Request-Headers: Authorization, X-Custom-Header
Origin: https://yourdomain.com

the mock responds with:

HTTP/1.1 200 OK
Access-Control-Allow-Origin: *
Access-Control-Allow-Methods: POST
Access-Control-Allow-Headers: Authorization,X-Custom-Header

To learn more about how CORS works, see these articles on MDN:

Cross-Origin Resource Sharing (CORS)

Preflight request