text: import union from '.'
  
  test('returns concatenated array of two with only unique values', () => {
    const func = function() { return 'a' }
    const func2 = function() { return 'a' }
    const a = ['1', func, 2, 2, 3, false]
    const b = [1, 2, 3, false, 4, func, '1', func2]
  
    // 'a' array itself and then only unique values from 'b' array
    const result = ['1', func, 2, 3, false, 1, 4, func2]
    const result2 = [1, 2, 3, false, 4, func, '1', func2]
  
    expect(union(a, b)).toEqual(result)
    expect(union(a)(b)).toEqual(result)
  
    expect(union(b, a)).toEqual(result2)
    expect(union(b)(a)).toEqual(result2)
  })
  
  test('do not mutate arrays', () => {
    const a = [1, 2, 3]
    const b = [2, 3, 4]
  
    union(a, b)
  
    expect(a).toEqual([1, 2, 3])
    expect(b).toEqual([2, 3, 4])
  })
  