message: update FlexItem test
diff: @@ -2,12 +2,23 @@ import React from 'react'
  import Flex from '../Flex'
  import {FLEX} from '../constants'
  import {render} from '../utils/testing'
  +import {render as HTMLRender, cleanup} from "@testing-library/react";
  +import {axe, toHaveNoViolations} from 'jest-axe'
  +import 'babel-polyfill'
  +expect.extend(toHaveNoViolations)
  describe('Flex.Item', () => {
  it('implements system props', () => {
  expect(Flex.Item).toImplementSystemProps(FLEX)
  })
  + it('should have no axe violations', async () => {
  + const {container} = HTMLRender(<Flex.Item />)
  + const results = await axe(container)
  + expect(results).toHaveNoViolations()
  + cleanup()
  + })
  +
  it('has default theme', () => {
  expect(Flex.Item).toSetDefaultTheme()
  })
  