Swagger/OpenAPI mock server

Question

I have an API reference in a Swagger file. I want to create a very simple mock server, so that when I call e.g.:

mymockurl.com/users it will return a predefined JSON (no need to connect to a database).

What's the easiest way to do this? I'm not a backend guy.

Answer 1

An easy way to create simple mock from an OpenAPI (fka Swagger) spec without code is to use a tool call prism available at http://github.com/stoplightio/prism written in Typescript.

This command line is all you need:

./prism run --mock --list --spec <your swagger spec file>

The mock server will return a dynamic response based on the OpenAPI spec. If examples are provided in the spec, prism will return them, if not it will generate dummy data based on the spec.

Edit (Aug 2020):

The command has changed in the latest version. The following will do:

prism mock <your spec file>

It accepts swagger and postman doc as well.

Answer 2

SwaggerHub provides a mock server for OpenAPI 2.0 and 3.0 specs. Mocking is supported on both free and paid plans.

To use the mock server, import your spec into SwaggerHub and enable "API Auto Mocking". Mock responses can be JSON, YAML and XML, and are generated based on your response schemas and the example, default and enum values defined in the schemas.

Disclosure: I work for the company that makes SwaggerHub.

Answer 3

Imposter is a a scriptable, multipurpose mock server written in Java.

Very easy to setup in a Docker environment and provides a Swagger UI to play with your mock api.

Let's see an example setup

1. Have a swagger configuration ready in a file in the folder config/petstore.yaml

    swagger: "2.0"
    info:
    version: 1.0.0
    title: Swagger Petstore
        .
        .
        .
   

You can copy the example swagger specification from here.

2. Create a configuration file for Imposter in config/openapi-plugin-petstore-config.json

    {
      "plugin": "com.gatehill.imposter.plugin.openapi.OpenApiPluginImpl",
      "specFile": "petstore.yaml"
    }
   

   Name of the configuration file has to end with -config.json.

3. Run Imposter with Docker

   Ensure that your shell is placed in the parent directory of config and run

    docker run -ti -p 8443:8443 \
    -v $(pwd)/config:/opt/imposter/config \
    outofcoffee/imposter-openapi
   

4. Open http://localhost:8443/_spec/ to play with your Mock Server and Swagger UI

   

Answer 4

Given the OpenAPI/Swagger spec, you can use Swagger Codegen to generate server stub in different server frameworks (e.g. Java Spring. PHP Slim, Ruby on Rails5, etc).

Here is the related documentation:

https://github.com/swagger-api/swagger-codegen/wiki/Server-stub-generator-HOWTO

UPDATE: In May 2018, about 50 top contributors of Swagger Codegen decided to fork the project to create a community-driven version called OpenAPI Generator. Please refer to the Q&A for the reasons behind the fork.

Answer 5

Here is the docker container for mock api server from swagger yaml.

docker run -i \
    -p 8000:8000 \
    -v /path/to/file.yaml:/data/swagger.yaml \
    -t palo/swagger-api-mock:latest

This is internally using swagger-mock-api

Answer 6

Mock Server project supports creating stubs based on Swagger/OpenAPI Specs.

https://www.mock-server.com/mock_server/using_openapi.html

Answer 7

I docker composed Swagger Editor, Swagger UI and Swagger mock api server to handle them more easily. Check it out. There is a sample swagger spec in this so the Editor, UI and the mock API server will run without any configuration from the start. All you need to do is edit the swagger spec, save swagger.json and swagger.yaml, and restart docker.

swagger-all-in-one-docker-compose

Answer 8

I created mock api server myself that can server swagger.json file. It is very easy to setup locally if you have python installed.

Have a look at this: https://github.com/bikcrum/Mock-API-server

Just use this command to serve your swagger.json file which will create API endpoints based on specification on the swagger file.

Quick and straightforward

python app.py -s /path/to/swagger.json

Extended options

usage: app.py [-h] -s SOURCE [-p PORT] [-t {swagger}] [-sc STATUS_CODE] [-r RANDOM_SEED] [-d DEFAULT_VALUE [DEFAULT_VALUE ...]]
              [-l LIST_SIZE [LIST_SIZE ...]]

Options for mock responses

Required and optional arguments:
  -h, --help            show this help message and exit

  -s SOURCE, --source SOURCE
                        (Required) API reference source file path.
  
  -p PORT, --port PORT  (Optional,default=5000) Port number the app runs on.

  -t {swagger}, --type {swagger}
                        (Optional,default='swagger') Type of API reference. Currently only supports Swagger.

  -sc STATUS_CODE, --status_code STATUS_CODE
                        (Optional,default=200) Generates responses with status code provided.

  -r RANDOM_SEED, --random_seed RANDOM_SEED
                        (Optional) Generates random responses based on seed value.

  -d DEFAULT_VALUE [DEFAULT_VALUE ...], --default_value DEFAULT_VALUE [DEFAULT_VALUE ...]
                        (Optional) Sets default values in response body. Format key=value.

  -l LIST_SIZE [LIST_SIZE ...], --list_size LIST_SIZE [LIST_SIZE ...]
                        (Optional,default=[2]) Sets default size of list in response body.

Answer 9

Recently I have come across Microcks.io and it has helped me solve number of problems. Also found Apicur.io for editing/creating swagger files. A standard worth embrasing.

Answer 10

Specmatic lets you create a mock server with your OpenAPI Specifications (Please see video demo). Here is the "getting started" guide.

An important aspect to consider while creating mock servers is that the canned responses / expectations / stub data that you setup should never go out of sync with your OpenAPI Specifications (Stale Stubs). This is guaranteed with Specmatic Smart Mocks.

Disclosure: I am lead developer and CTO at Specmatic

Answer 11

Use Mockoon, "Mockoon is the easiest and quickest way to design and run mock REST APIs. No remote deployment, no account required, free and open-source." It has the best user-friendly GUI in my opinion. It also has a CLI and Serverless function option. You can generate mock endpoints from your Swagger/Open API files and export them after you've made changes.

There are many other features: Multiple responses per route, File serving, etc. See https://mockoon.com/features/ for details.

You can see Mockoon's comparison to other products here: https://mockoon.com/compare/

Answer 12

MockLab now supports auto-generation of mock APIs from an imported Swagger definition. And you can also set it up as a webhook received in Swaggerhub so it gets updated on every save/publish:

https://www.mocklab.io/blog/mocklab-now-supports-swagger-and-swaggerhub/

Answer 13

openapi-mock is a CLI wrapper for swagger-node-runner and sway specifically to start a mock server from an openapi/swagger spec file.