parrot-middleware

parrot-middleware

parrot-middleware is an implementation of Parrot that can be used as an Express middleware.

Given a collection of Parrot scenarios which each have a list of request and response pairs, the parrot middleware will intercept the requests that match the paths in the active scenario. The middleware will also expose 3 additional routes which are detailed below: GET /parrot/scenario, POST /parrot/scenario, GET /parrot/scenarios.

Example

Let's walk through how to set up some scenarios using the parrot-middleware.

Define your scenarios

Add a file to the root of your project called scenarios.js:

// scenarios.js
const scenarios = {
  'has one ship': [
    {
      request: '/ship_log',
      response: {
        body: [{ name: 'The Jolly Roger', captain: 'Captain Hook' }],
      },
    },
  ],
  'has more ships': [
    {
      request: '/ship_log',
      response: {
        body: [
          { name: 'The Jolly Roger', captain: 'Captain Hook' },
          { name: 'The Black Pearl', captain: 'Jack Sparrow' },
          { name: 'Flying Dutchman', captain: 'Davy Jones' },
          { name: 'The Wanderer', captain: 'Captain Ron' },
        ],
      },
    },
  ],
  'has more ships with any mime type': [
    {
      request: '/ship_log',
      response: {
        contentType: 'text/plain',
        body: [
          '# Ship Log',
          "* name: 'The Jolly Roger', captain: 'Captain Hook'",
          "* name: 'The Black Pearl', captain: 'Jack Sparrow'",
        ].join('\n'),
      },
    },
  ],
  'has a server error': [
    {
      request: '/ship_log',
      response: {
        status: 500,
      },
    },
  ],
};

export default scenarios;

This file has three scenarios: has one ship, has more ships, and has a server error. Each scenario is mocking a single request: /ship_log. This means that depending on which scenario is active, hitting /ship_log will return different responses.

Providing the middleware

Now let's create a tiny web server. Add a file named server.js to the root of your project. Make sure that you npm install express parrot-middleware before running server.js:

// server.js
import express from 'express';
import parrot from 'parrot-middleware';
import scenarios from './scenarios';

const app = express();

app.use(parrot(scenarios));

app.listen(3001);

Setting the active scenario

Let's get our server running. Run node server.js from the command line, which will spin up our tiny web server on http://localhost:3001.

Now that our server is running, we can set the active scenario by sending a POST request to http://localhost:3001/parrot/scenario with a JSON payload that contains a single key/value pair "scenario": "<scenario name>". Let's activate one of our scenarios:

POST http://localhost:3001/parrot/scenario
Content-Type: application/json

{
  "scenario": "has one ship"
}

We can verify that the active scenario is now has one ship by simply submitting a GET request to the same URL: http://localhost:3001/parrot/scenario.

Now that "has one ship" is the active scenario, navigating to http://localhost:3001/ship_log will return [{ name: 'The Jolly Roger', captain: 'Captain Hook' }].

Try setting the active scenario to has more ships and see if you get the expected response in our scenarios!

Inspect scenarios

If you'd like to see exactly how the scenarios are parsed and view more details as to what the expected response will be, you can send a GET request to http://localhost:3001/parrot/scenarios, which for us would return:

[
  {
    name: 'has one ship',
    mocks: [
      {
        request: {
          path: '/ship_log',
          method: 'GET',
        },
        response: {
          status: 200,
          body: [
            {
              name: 'The Jolly Roger',
              captain: 'Captain Hook',
            },
          ],
        },
      },
    ],
  },
  {
    name: 'has more ships',
    mocks: [
      {
        request: {
          path: '/ship_log',
          method: 'GET',
        },
        response: {
          status: 200,
          body: [
            {
              name: 'The Jolly Roger',
              captain: 'Captain Hook',
            },
            {
              name: 'The Black Pearl',
              captain: 'Jack Sparrow',
            },
            {
              name: 'Flying Dutchman',
              captain: 'Davy Jones',
            },
            {
              name: 'The Wanderer',
              captain: 'Captain Ron',
            },
          ],
        },
      },
    ],
  },
  {
    name: 'has a server error',
    mocks: [
      {
        request: {
          path: '/ship_log',
          method: 'GET',
        },
        response: {
          status: 500,
        },
      },
    ],
  },
];

Using Scenarios

For ease of use, you may want to check out the Parrot Devtool Chrome Plugin, which will provide an easy to use interface for interacting with the endpoints above.