Chai JSON pattern assertions

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Chai JSON Pattern
Deep matching objects with clear, JSON-like syntax.

Chai JSON pattern allows you to create blueprints for JavaScript objects to ensure validation of key information. It enables you to use JSON syntax extend with easy to use validators. It came up mostly for testing API with cucumber-js, but can be used in any application. Additionaly you can extend base functionality with custom validators. For more information see API reference.
See the detailed API Reference.
const pattern = `
        "username": String AND alphanum AND minLength(3) AND maxLength(30),
        "password": String AND regex("/^[0-9a-zA-Z]{5,30}$/"),
        "access_token"?: String AND Number,
        "birthyear": Integer AND range(1900, 2017),
        "email": String,

The above pattern require user to be an object with keys that satisfy following conditions:
  • username
* required string
* contain only alphanumeric characters
* must have at least 3 characters, and maximum 30
  • password
* required string
* must satisfy the custom regex
  • access_token
* optional string or number
  • birthyear
* required Integer between 1900 and 2017
  • email
* required string
  • allow another keys (e.g. createdAt, updateAt, etc.)

If user will not satisfy pattern, test will not pass, and you will see error with diff between user and pattern.
Usage is a two steps process. First, you have to install chai-json-pattern package.
npm run --save-dev chai-json-pattern
Then import chaiJsonPattern and use matchPattern:
import chai, { expect } from 'chai';
import chaiJsonPattern from 'chai-json-pattern';


expect({ a: 2 }).to.matchPattern(`{
    "a": Number AND range(0, 5),