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)})