text: import once from '.'
  
  test('returns function, that could be invokated only once and will return that value every time', () => {
    var addOne = x => x + 1
    var wrapped = once(addOne)
    var res1 = wrapped(1)
    var res2 = wrapped(10)
  
    expect(res1).toBe(2)
    expect(res2).toBe(2)
  })
  
  test('supports functions of any arity', () => {
    var sum1 = once((x, y) => x + y)
    var sum2 = once((x, y, z) => x + y + z)
  
    expect(sum1(1, 1)).toBe(2)
    expect(sum1(2, 2)).toBe(2)
  
    expect(sum2(1, 1, 1)).toBe(3)
    expect(sum2(2, 2, 2)).toBe(3)
  })
  