openapi-mock-express-middleware

Generates express mock-servers from Open API 3.0 specs.

Installation

To begin, you'll need to install openapi-mock-express-middleware:

$ npm install openapi-mock-express-middleware --save-dev

Usage

Simple Config

const express = require('express');
const { createMockMiddleware } = require('openapi-mock-express-middleware');

const app = express();

app.use(
  '/api', // root path for the mock server
  createMockMiddleware({ spec: '/absolute/path/to/your/openapi/spec.yml' }),
);

app.listen(80, () => console.log('Server listening on port 80'));

Advanced Config

The middleware uses json-schmea-faker under the hood. To configure it, you can pass the options object to the factory function. (The full list of available options can be seen here)

const express = require('express');
const { createMockMiddleware } = require('openapi-mock-express-middleware');

const app = express();

app.use(
  '/api',
  createMockMiddleware({
    spec: '/absolute/path/to/your/openapi/spec.yml', // string or OpenAPIV3.Document object
    options: { // json-schema-faker options
      alwaysFakeOptionals: true,
      useExamplesValue: true,
      randomizeExamples: true, // choose a random example from the examples object; when set to false (default) the first example is used
      // ...
    },
    configure: (jsf) => {
    	// function where you can extend json-schema-faker
    	...
    }
  }),
);

app.listen(80, () => console.log('Server listening on port 80'));

Mock data

Basic behavior

By default midleware generates random responses depending on the types specified in the openapi docs.

doc.yml

...
paths:
  /company
    get:
      responses:
        '200':
          content:
            application/json:
              schema:
                type: object
                required:
                  - id
                  - number
                properties:
                  id:
                    type: string
                  number:
                type: integer
...

GET /company response

{
  id: 'dolor veniam consequat laborum',
  number: 68385409.
}

Faker or Chance generated responses

In addition faker.js or chance.js methods can be specified for data generation. In order to use these generators you have to configure middleware through the configure option of the factory function.

const express = require('express');
const { createMockMiddleware } = require('openapi-mock-express-middleware');
import faker from '@faker-js/faker';
import Chance from 'chance';

const app = express();

app.use(
  '/api',
  createMockMiddleware({
    spec: '/absolute/path/to/your/openapi/spec.yml',
    configure: (jsf) => {
    	jsf.extend('faker', () => faker);
	jsf.extend('chance', () => new Chance());
    }
  }),
);

app.listen(80, () => console.log('Server listening on port 80'));

After that you can use 'x-faker' and/or 'x-chance' attributes in your openapi specs.

spec.yml

...
paths:
  /user
    get:
      responses:
        '200':
          content:
            application/json:
              schema:
                type: object
                required:
                  - id
                  - name
                properties:
                  id:
                    type: string
                    x-faker: random.uuid
                  name:
                    type: string
                    x-faker: name.findName
                  email:
                    type: string
                    x-chance:
                      email:
                        domain: fake.com	  
...

GET /user response

{
  id: '8c4a4ed2-efba-4913-9604-19a27f36f322',
  name: 'Mr. Braxton Dickens',
  email: '[email protected]'
}

Responses generated from examples

If an example for the response object is specified, it will be used as a resulting sever response.

doc.yml

...
paths:
  /user
    get:
      responses:
        '200':
          content:
            application/json:
              schema:
                type: object
                example:
                  id: 'id-125'
                  name: 'John Smith'
                required:
                  - id
                  - name
                properties:
                  id:
                    type: string
                    x-faker: random.uuid
                  name:
                    type: string
                    x-faker: name.findName
...

GET /user response

{
  id: 'id-125',
  name: 'John Smith'.
}

If multiple examples for the response object are specified, the first one will be used as a resulting sever response.

doc.yml

...
paths:
  /user
    get:
      responses:
        '200':
          content:
            application/json:
              schema:
                type: object
                examples:
                  first:
                    value:
                      id: 'id-125'
                      name: 'John Smith'
                  second:
                    value:
                      id: 'some-other-id'
                      name: 'Joe Doe'
                required:
                  - id
                  - name
                properties:
                  id:
                    type: string
                    x-faker: random.uuid
                  name:
                    type: string
                    x-faker: name.findName
...

GET /user response

{
  id: 'id-125',
  name: 'John Smith'.
}

If you want to use some other logic for generating responses from the examples attributes you can easily implement it by overwriting this behavior in the configure option of the middleware's factory function:

const express = require('express');
const { createMockMiddleware } = require('openapi-mock-express-middleware');

const app = express();

app.use(
  '/api',
  createMockMiddleware({
    spec: '/absolute/path/to/your/openapi/spec.yml',
    configure: (jsf) => {
      jsf.define('examples', (value) => {
        if (typeof value === 'object' && value !== null && Object.keys(value).length) {
          return value[Object.keys(value)[0]].value;
        }

        return '';
      });
    }
  }),
);

app.listen(80, () => console.log('Server listening on port 80'));

Contributing

Please take a moment to read our contributing guidelines if you haven't yet done so.

CONTRIBUTING

License

MIT