Chai.js expectations cheatsheet

chaijs-cheatsheet.js

// instead of using `expect(object).to.exist`, assert things
// through `.to.be.a(type)` which make failures more informative
expect(result).to.be.an('object')
  .that.includes({
    foo: 'bar',
    baz: 'quux'
  });

// to assert property value types i.e. date:
expect(result)
  .to.have.property('createdAt')
  .that.is.a('date');

// to assert errors:
expect(err).to.be.an('error')
  .with.property('message', 'Oops!');

// to assert promises (thenable):
expect(result)
  .to.be.an('object')
  .with.property('then')
  .that.is.a('function');