message: add Box test
diff: @@ -3,8 +3,20 @@ import Box from '../Box'
  import theme from '../theme'
  import {render} from '../utils/testing'
  import {LAYOUT, COMMON} from '../constants'
  +import {render as HTMLRender, cleanup} from "@testing-library/react";
  +import {axe, toHaveNoViolations} from 'jest-axe'
  +import 'babel-polyfill'
  +expect.extend(toHaveNoViolations)
  +
  describe('Box', () => {
  + it("should have no axe violations", async () => {
  + const {container} = HTMLRender(<Box/>)
  + const results = await axe(container)
  + expect(results).toHaveNoViolations()
  + cleanup()
  + })
  +
  it('implements system props', () => {
  expect(Box).toImplementSystemProps(LAYOUT)
  expect(Box).toImplementSystemProps(COMMON)
  