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import { concat } from './concat'
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')).toEqual('ABCDEF')})