Chai.js-Cheatsheet

Assert

assert(val)
assert.fail(actual, expected)
assert.ok(val)                        // is truthy
assert.equal(actual, expected)        // compare with ==
assert.strictEqual(actual, expected)  // compare with ===
assert.deepEqual(actual, expected)    // deep equal check
assert.isTrue(val)
assert.isFalse(val)
assert.isNull(val)
assert.isNotNull(val)
assert.isUndefined(val)
assert.isDefined(val)
assert.isFunction(val)
assert.isObject(val)
assert.isArray(val)
assert.isString(val)
assert.isNumber(val)
assert.isBoolean(val)
assert.typeOf(/tea/, 'regexp') // Object.prototype.toString()
assert.instanceOf(chai, Tea)
assert.include([ a,b,c ], a)
assert.match(val, /regexp/)
assert.property(obj, 'tea') // 'tea' in object
assert.deepProperty(obj, 'tea.green')
assert.propertyVal(person, 'name', 'John')
assert.deepPropertyVal(post, 'author.name', 'John')
assert.lengthOf(object, 3)
assert.throws(function() { ... })
assert.throws(function() { ... }, /reference error/)
assert.doesNotThrow
assert.operator(1, '<', 2)
assert.closeTo(actual, expected)
See: Assert API (chaijs.com)

BDD syntax

const { expect } = require('chai')
expect(object)
  .to.equal(expected)
  .to.eql(expected)        // deep equality
  .to.deep.equal(expected) // same as .eql
  .to.be.a('string')
  .to.include(val)
  .be.ok(val)
  .be.true
  .be.false
  .to.exist
  .to.be.null
  .to.be.undefined
  .to.be.empty
  .to.be.arguments
  .to.be.function
  .to.be.instanceOf
  .to.be.gt(5)  // aka: .above .greaterThan
  .to.be.gte(5) // aka: .at.least
  .to.be.lt(5)  // aka: .below
  .to.respondTo('bar')
  .to.satisfy((n) => n > 0)
  .to.have.members([2, 3, 4])
  .to.have.keys(['foo'])
  .to.have.key('foo')
  .to.have.lengthOf(3)
expect(() => { ··· })
  .to.throw(/not a function/)
See: BDD (chaijs.com)

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