moy-fp/test/Object/lensIndex.test.js

A functional programming library.

import __ from '../../src/Function/__'
import Identity from '../../src/Functor/Identity/index'
/**
 * Number -> Lens s a
 * Lens s a = Functor f => (a -> f a) -> s -> f s 
 */
import lensIndex from '../../src/Object/lensIndex'

/**
 * you should not use this similar funciton to get value anywhere in your application
 * if you must need the inner value, you may need Comonad
 * here is just simple for test
 */
const inspect = x => `Identity(${JSON.stringify(x.value)})`

test('lensIndex(not using __), not execute', () => {
  expect(
    lensIndex(-1)
  ).toEqual(expect.any(Function))
})

test('lensIndex(not using __), execute', () => {
  expect(
    inspect(lensIndex(-1)(Identity)([1, 2, 3, 4]))
  ).toBe('Identity([1,2,3,4])')
})


test('lensIndex(using __), not execute', () => {
  expect(
    lensIndex(__)(-1)
  ).toEqual(expect.any(Function))
})