1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
import { concat } from './concat.js'
test('happy', () => {  const arr1 = [ 'a', 'b', 'c' ]  const arr2 = [ 'd', 'e', 'f' ]
  const a = concat(arr1, arr2)  const b = concat(arr1)(arr2)  const expectedResult = [ 'a', 'b', 'c', 'd', 'e', 'f' ]
  expect(a).toEqual(expectedResult)  expect(b).toEqual(expectedResult)})
test('with strings', () => {  expect(concat('ABC', 'DEF')).toBe('ABCDEF')})