xassert

xassert - Extensible Assertions

Homepage

Just another assertion library inspired by Chai Assertion Library and Java Hamcrest with interesting features:

• Extensible
• No complex property chains (e.g is.not.equal)
• No property terminators (e.g. is.true) that could deliver false positives on a typographic error.
• Promises support
• Property assertion chaining

Install

npm install xassert --save-dev
# or
npm install xassert

Simple example

const assert = require('xassert')
const result = 'banana'
assert(result).isEqualTo('banana')

Chaining

const assert = require('xassert')

assert(obj)
  .hasOwnProperty('a').andIt
  .hasOwnProperty('b', it => it.isEqualTo('john'))

How to extend

// CommonJS
const assert = require('xassert')
const { Assertion, AssertionError } = assert
// Or
import assert, { Assertion, AssertionError } from xassert

const banana = 'I am a banana!'
const apple = 'I am an apple'
// Add a new method
Assertion.prototype.isABanana = function isABanana () {
  if (this.actual !== banana) throw this.fire('{name} is not a banana', banana)
  return this
}

assert(banana).isABanana()
assert(() => assert(apple).isABanana()).throwsAn(AssertionError)