Hazy

Lazy JSON fixtures in Node

---

Hazy aims to ease the hassle of generating, maintaining and working with fixtures by making them DRY and more expressive. Hazy lets developers describe and generate test data in a normailzed fasion and allows for fixtures to be processed further at run-time for increased flexibility.

Features

• Simple syntax for supporting both normalized and random data in fixtures
• DRY, embeddable, and queryable fixtures / sub-fixtures
• Random String, Number and Date data via ChanceJS
• Lazy processing via run-time queries (JsonPath)

Design Goals

• Non-invasive (retain all involved standards, especially JSON)
• Unique and identifiable syntax
• Convention based, interpreter agnostic
• Pre-processed, but optionally evaluated at run-time
• Cleanly integrate with all Node testing frameworks

Example

Here we register a couple of JSON fixtures into what's refered to as the fixture pool:

import hazy from 'hazy'
 
hazy.fixture.register('someDude', {
  id    : '|~misc.guid|',
  name  : '|~person.prefix| |~person.name|',
  email : '|~web.email|',
  bday  : '|~person.birthday|',
  ssn   : '|~person.ssn| (not really)',
})
 
/* loads someDog.json (assumes .json extension when none is provided), containing:
{
  id    : '|~misc.guid|',
  owner : '|*someDude|'
  name  : 'Dawg',
}*/
hazy.fixture.src('someDog')
 
const hazyDude = hazy.fixture.get('someDude')
const hazyDog  = hazy.fixture.get('someDog')

The processed fixtures result as follows:

// hazyDude
{
  id: 'e76de72e-6010-5140-a270-da7b6b6ad2d7',
  name: 'Mr. Agnes Hammond',
  bday: Wed Apr 27 1994 04:05:27 GMT-0700 (Pacific Daylight Time),
  ssn: '264-66-4154 (not really)'
}
 
// hazyDog
{
  id: '427b2fa6-02f8-5be5-b3d1-cdf96f432e28',
  name: 'Dawg',
  owner: {
    id: 'e76de72e-6010-5140-a270-da7b6b6ad2d7',
    name: 'Mr. Agnes Hammond',
    bday: Wed Apr 27 1994 04:05:27 GMT-0700 (Pacific Daylight Time),
    ssn: '264-66-4154 (not really)'
  }
}

Installation

> npm install hazy

if you wish to develop:

> git clone http://github.com/slurmulon/hazy.git
> cd hazy
> npm link hazy

Test

> cd hazy

then

> npm test

Documentation

The following provides a high-level summary of all of Hazy's features as well as some examples and gotchas.

A notable observation is that Hazy's syntax can be expressed quite simply:

|<operator> <expression|statement>|

Supported operators are:

• ~ generate random data
• * embed fixture data from pool
• $ query by JsonPath pattern and embed fixture from pool
• @ find and embed fixture from filesystem
• ? find and embed fixture from pool or filesystem
• > evaluate content as literal JavaScript
• = interpolate expression result

(more thorough documentation on the way)

Randomness

Hazy sits on top of ChanceJS, a great library for generating all sorts of useful random data. Hazy categorizes ChanceJS's generation methods for a more symantic syntax, but otherwise integration is completely transparent.

The token for generating random data is ~:

|~ <class>.<type>|

Random Data Tokens

• |~basic.<type>|

  supports 'bool', 'character', 'integer', 'natural', 'string'

• |~text.<type>|

  supports 'paragraph', 'sentence', 'syllable', 'word'

• |~person.<type>|

  supports 'age', 'birthday', 'cpf', 'first', 'gender', 'last', 'name', 'prefix', 'ssn', 'suffix'

• |~mobile.<type>|

  supports 'android_id', 'apple_token', 'bb_pin', 'wp7_anid', 'wp8_anid2'

• |~web.<type>|

  supports 'color', 'domain', 'email', 'fbid', 'google_analytics', 'hashtag', 'ip', 'ipv6', 'klout', 'tld', 'twitter', 'url'

• |~geo.<type>|

  supports 'address', 'altitude', 'areacode', 'city', 'coordinates', 'country', 'depth', 'geohash', 'latitude', 'longitude', 'phone', 'postal', 'province', 'state', 'street', 'zip'

• |~time.<type>|

  supports 'ampm', 'date', 'hammertime', 'hour', 'millisecond', 'minute', 'month', 'second', 'timestamp', 'year'

• |~misc.<type>|

  supports 'guid', 'hash', 'hidden', 'n', 'normal', 'radio', 'rpg', 'tv', 'unique', 'weighted'

Embedding

Hazy supports referencing and embedding other JSON fixtures (or really any value) present in the fixture pool using the * operator.

|* <fixture-pool-key>|

The someDog example above already shows how this is used:

hazy.fixture.register('someDog', {
  id    : '|~misc.guid|',
  owner : '|*someDude|'
  name  : 'Dawg',
})

the above will resolve to the following provided that someDude is in the fixture pool:

{
  id: '427b2fa6-02f8-5be5-b3d1-cdf96f432e28',
  name: 'Dawg',
  owner: {
    id: 'e76de72e-6010-5140-a270-da7b6b6ad2d7',
    name: 'Mr. Agnes Hammond',
    bday: Wed Apr 27 1994 04:05:27 GMT-0700 (Pacific Daylight Time),
    ssn: '264-66-4154 (not really)'
  }
}

Hazy also supports more advanced ways of embedding fixtures using queries, but more on that will follow in the next section.

Queries

Hazy utilizes JsonPath for defining functionality to pre-processed fixtures in a query-like fasion. Details on JsonPath can be found at http://goessner.net/articles/JsonPath/. There are many ways in which JSON objects can be queried using this flexible technique.

A primary goal of Hazy is to give developers both fine grained and generalized control over the data and functionality relevant to their fixtures.

Take our someDog fixture, for example:

{
  id: '427b2fa6-02f8-5be5-b3d1-cdf96f432e28',
  name: 'Dawg',
  owner: {
    id: 'e76de72e-6010-5140-a270-da7b6b6ad2d7',
    name: 'Mr. Agnes Hammond',
    bday: Wed Apr 27 1994 04:05:27 GMT-0700 (Pacific Daylight Time),
    ssn: '264-66-4154 (not really)'
  }
}

We can obtain the id of the dog's owner with the following query:

$.owner.id

After the fixture has been queried, this will result with:

e76de72e-6010-5140-a270-da7b6b6ad2d7

Embedded Queries

JsonPath expressions that match against the fixture pool can be specified with the query operator $. The results of the expression and will be embedded into the fixture upon processing. The syntax for embedded queries is:

|$ <jsonpath-expression>|

where <jsonpath-expression> is a valid JsonPath expression (minus the leading '$')

Note: Embedded queries (i.e. those defined outside of the lazy matcher pool hazy.matcher, particularly in source *.json files/data) are not and cannot be lazily evaluated because:

1. Very high risk of cyclic dependencies and infinite recursion (e.g., some fixtures may need to be lazily evaluated if they have not already been, potentially triggering an endless cycle)
2. Applying queries to pre-processed fixtures allows for cleaner queries (since you can query against Hazy tags) and provides consistent results. If queries were applied to post-processed fixtures, they would be bottlenecked to only working with properties since the processed random values are obviously inconsistent.

See the section on Lazy Query Matchers for a pragmatic and idiomatic solution to the issue.

Use of the operator is straight forward:

hazy.fixture.register('someShark', {
  id   : '|~misc.guid|',
  name : 'Tiger Shark',
  ate  : '|$.id|', // queries pool for any fixture with an "id" property at the highest level
})

this will result with something like:

{ 
  id: '64af61f8-daa8-5959-8be4-bdd536ecc5bd',
  name: 'Tiger Shark',
  ate: 
    [ { 
        id: 'e76de72e-6010-5140-a270-da7b6b6ad2d7',
        name: 'Mr. Agnes Hammond',
        bday: Wed Apr 27 1994 04:05:27 GMT-0700 (Pacific Daylight Time),
        ssn: '264-66-4154 (not really)'
      },
      { 
        id: '427b2fa6-02f8-5be5-b3d1-cdf96f432e28',
        name: 'Dawg',
        owner: {
          id: 'e76de72e-6010-5140-a270-da7b6b6ad2d7',
          name: 'Mr. Agnes Hammond',
          bday: Wed Apr 27 1994 04:05:27 GMT-0700 (Pacific Daylight Time),
          ssn: '264-66-4154 (not really)'
        }
      } 
    ] 
}

Note: The query operator currently always returns an Array. I consider this a limitation because it makes it difficult to integrate queries with other expressions. I hope to address this issue soon.

The only known limitation on the nesting depth of embedded fixtures is the stack size of the process. I have not pushed this limitation very far at all, but if any issues are encountered then please open an issue on Github.

Lazy Query Matchers

With Hazy we can leverage this powerful query mechanism in any Node environment to provide test-specific functionality to your fixtures. This is achieved by monkey-patching fixtures in the pool that match a specific JsonPath pattern.

For example, if we wanted to query our fixture pool for any fixture with an owner object containing an id property and then update those fixtures with new bark() functionality, then we would use the following:

hazy.matcher.config({
  path   : '$.owner.id',
  handle : (fixture, matches, pattern) => {
    // return the fixture after mutating it (if you so desire)
    return Object.assign({
      hasOwner : true,
      bark : () => {
        console.log('woof woof, my owner is ', matches[0])
      }
    }, fixture)
  }
})
 
hazy.fixture.register('someDogWithOwner', {
  id    : '|~misc.guid|',
  owner : '|*someDude|'
  name  : 'Happy Dog',
})
 
hazy.fixture.register('someDogWithoutOwner', {
  id   : '|~misc.guid|',
  name : 'Lonely Dog'
})
 
const happyDog  = hazy.fixture.get('someDogWithOwner')
const lonelyDog = hazy.fixture.get('someDogWithoutOwner')

Since the matcher only applies to fixtures with an owner id, only happyDog will contain the hasOwner property and a bark method:

happyDog.bark()

woof woof, my owner is e76de72e-6010-5140-a270-da7b6b6ad2d7

lonelyDog.bark()

Error: undefined is not a method

---

This feature can also be combined with hazy.fork() so that query matchers can be scoped to a particular state of the fixture pool. Any query matcher defined at a higher scope can be easily and safely overwritten in a Hazy fork:

hazy.matcher.config({
  path   : '$.owner.id',
  handle : (fixture, matches, pattern) => {
    // return the fixture after mutating it (if you so desire)
    return Object.assign({
      hasOwner : true,
      bark : () => {
        console.log('woof woof, my owner is ', matches[0])
      }
    }, fixture)  
  }
})
 
hazy.fixture.register('someDogWithOwner', {
  id    : '|~misc.guid|',
  owner : '|*someDude|'
  name  : 'Happy Dog',
})
 
const happyDog  = hazy.fixture.get('someDogWithOwner')
let   sleepyDog = null
 
function forkTest() {
  const newHazy = hazy.fork()
 
  newHazy.matcher.config({
    path   : '$.owner.id',
    handle : (fixture) => {
      fixture.bark = () => {
        console.log('zzzz, too tired')
      }
      
      return fixture
    }
  })
 
  sleepyDog = newHazy.fixture.get('someDogWithOwner')
}
 
forkTest()

and now...

happyDog.bark()

still prints woof woof, my owner is e76de72e-6010-5140-a270-da7b6b6ad2d7, while

sleepyDog.bark()

now prints zzzz, too tired, overriding the matcher defined at a higher context level (AKA happyDog's) safely

Lastly, you have some control over when evaluation occurs:

• hazy.fixture.get will apply any pattern-matched functionality to the relevant fixture each time it is called.
• hazy.fixture.lazyGet applies any pattern-matched functionality to the relevant fixture, but only does so once (memoized).

Both implementations are technically lazy since their evaluation is deferred until the last minute, but lazyGet is even more so since it only runs once.

Scripting

Hazy also evaluates text through a lodash interpolation template. This enables you to include JavaScript expressions in your fixtures.

This is an experimental feature, so use it with caution.

Interpolate

Insert the result of an expression. The fixture pool and random data factories are all available as variables.

Specified with the = operator.

hazy.lang.process('{"random_point": "|= random.basic.integer({min: 0, max: 100})|"}')

As a convenience, ES6's interpolation syntax can also be used:

hazy.lang.process('{"random_point": "${random.basic.integer({min: 0, max: 100})}"}')

Evaluate

Evaluates content as JavaScript, allowing you to perform if statements, loops, etc.

Specified with the > operator.

hazy.lang.process('{"random_point": |> if (foo) {| |=random.basic.integer({min: 0, max: 100})| |> }|}', {foo: true})

TODO

• Silent/collapsed whitespace override (useful for loading fixtures into pool without having to print the contents)
• Array literal operator
• Seeds for random data
• Memoized/scoped random data
• Support JSON Pointer
• Support json-rel
• Remote fixtures via http
• CLI