import {compose} from './compose'import {keys} from './keys'import {lensIndex} from './lensIndex'import {over} from './over'import {set} from './set'import {view} from './view'
const testList = [{a: 1}, {b: 2}, {c: 3}]
test('focuses list element at the specified index', () => { expect(view(lensIndex(0), testList)).toEqual({a: 1})})
test('returns undefined if the specified index does not exist', () => { expect(view(lensIndex(10), testList)).toEqual(undefined)})
test('sets the list value at the specified index', () => { expect(set(lensIndex(0), 0, testList)).toEqual([0, {b: 2}, {c: 3}])})
test('applies function to the value at the specified list index', () => { expect(over(lensIndex(2), keys, testList)).toEqual([{a: 1}, {b: 2}, ['c']])})
test('can be composed', () => { const nestedList = [0, [10, 11, 12], 1, 2] const composedLens = compose(lensIndex(1), lensIndex(0))
expect(view(composedLens, nestedList)).toEqual(10)})
test('set s (get s) === s', () => { expect(set(lensIndex(0), view(lensIndex(0), testList), testList)).toEqual( testList )})
test('get (set s v) === v', () => { expect(view(lensIndex(0), set(lensIndex(0), 0, testList))).toEqual(0)})
test('get (set(set s v1) v2) === v2', () => { expect( view( lensIndex(0), set(lensIndex(0), 11, set(lensIndex(0), 10, testList)) ) ).toEqual(11)})