moy-fp/test/List/headList.test.js

A functional programming library.

import __ from '../../src/Function/__'
/**
 * [a] -> a | undefined
 */
import headList from '../../src/List/headList'

test('headList(not using __), not empty array', () => {
  expect(
    headList([1, 2, 3, 4])
  ).toBe(1)
})

test('headList(not using __), empty array', () => {
  expect(
    headList([])
  ).toBeUndefined()
})

test('headList(using __), not empty array', () => {
  expect(
    headList([1, 2, 3, 4])
  ).toBe(1)
})