text: const expect = require('expect.js')
  const union = require('../lib/union')
  
  describe('lib/union', () => {
    it('should accept only arrays as arguments', (done) => {
      expect(union).withArgs([1], 2).to.throwError()
      expect(union).withArgs([1], [2]).not.to.throwError()
      done()
    })
  
    it('should create a union of the values', (done) => {
      expect(union([1, 2], [2, 3])).to.eql([1, 2, 3])
      expect(union([1, 2, 3], [3, 5, 6], [3, 4, 7])).to.eql([1, 2, 3, 5, 6, 4, 7])
      done()
    })
  })
  