polaroid

A test snapshotting tool for API requests, based on Jest snapshot testing.

Why?

I really really really like Jest snapshot testing for React components, and after writing them for a while I realized it would be really useful for testing API responses, too. After all, API responses are big blocks of JSON alongside a status code and you want to be really sure those things never ever change. These are basically the ultimate API functional tests, in my opinion.

blah blah blah jump to the example code

Current Name

This is probably a bad idea for obvious reasons so I will probably rename it.

Usage

There are two functions you'll use with this library: the exported polaroid setup method, and the snap method used in tests.

polaroid()

First, call the polaroid function with some setup options, usually in a test suite's before hook, to get a copy of the snap function you can use in your tests.

describe('my test suite', function() {
  let snap
  
  before(function() {
    snap = polaroid(options)
  }

It takes a single options hash with the following possible keys:

app (required)

Your API app object, which can be anything that supertest says it can be. (As of now, it says: "You may pass an http.Server, or a Function to request() - if the server is not already listening for connections then it is bound to an ephemeral port for you so there is no need to keep track of ports.")

testFilePath (required)

The full path to the current test file, which will be used to name the snap file if it doesn't already exist. i.e. my-test.spec.js -> my-test.snap Note: this needs to be the full path to the file, not just the file name.

getName (optional)

Function that returns the name for a given snapshot. The mocha helper sets this to the name of the current it, which works really well. If you're not using mocha, you can figure out a different way to get that value or just skip this and pass in the snap names in each test directly.

snapsDirectory (optional)

By default, snap files get placed in a __snapshots__ directory next to the test file. If you want to override the directory where those files are placed, list a full path to a different directory here (say you want them all to go in /tests/snapshots or something).

logging (optional, default: true)

Whether or not to log messages about snapshot statuses (when a new one is created or updated, how to fix broken ones, etc.)

howToFix (optional)

Optional string that will be printed to the console (if logging is turned on) whenever a test fails, usually to tell the user how to autofix the snapshot.

autofix (optional, default false)

If true, broken snapshot tests will be rewritten and updated. You need to figure out how you want the user to do this -- in my example (below) it's by re-running the test suite with AUTOFIX=true prepended.

snap()

Use the snap function itself to create snapshots inside of tests. You should return the result of the snap function if your test runner respects promises for async tests (if you need some kind of done function, uh, PRs welcome and stuff)

it('should do some test things', function() {
  return snap({ method: 'GET', path: '/my/sweet/api' }) // tada
})

The snap function takes 2 arguments: some http options and some snap options.

HTTP options

These get converted to supertest chained methods. Right now they include:

method (required)

HTTP method for the request (e.g. GET, PUT, POST, DELETE)

path (required)

The (ahem) path of the request (e.g. /some/path)

body

Object representing the JSON body to be sent for PUT or POST requests.

Snap options

This argument is totally optional, as are all the keys inside this object:

name

If you didn't pass a getName function in earlier, or if you want to override it for some reason, you can pass the snap name here.

message

This is the message that assert will print if the snap didn't match the stored version. There's a default so this is probably not necessary.

Example

The full example is in the example folder (right?), which you can run by cloning the repo and running:

npm install && npm run examples

Here's basically what the example shows, but with a real API running:

const app = require('../app')
const polaroid = require('polaroid')
 
describe('example snapshot tests', function() {
 
  let snap
 
  before(function() {
    // not necessary to use mocha, but if you do, this works
    const { testFilePath, getName } = polaroid.mocha(this)
    snap = polaroid({
      app,
      testFilePath,
      getName,
      howToFix: 'Snapshot failed, to fix re-run with AUTOFIX=true',
      autofix: Boolean(process.env.AUTOFIX)
    })
  })
 
  it('should get a collection of people', function() {
    return snap({
      method: 'GET',
      path: '/example/people'
    })
  })
 
  it(`should create a new person`, function() {
    return snap({
      method: 'POST',
      path: '/example/people',
      body: {
        name: 'Jo',
        age: 19
      }
    })
  })
 
})