message: add Caret test
diff: @@ -2,12 +2,23 @@ import React from 'react'
  import Caret from '../Caret'
  import {render} from '../utils/testing'
  import theme from '../theme'
  +import {render as HTMLRender, cleanup} from "@testing-library/react";
  +import {axe, toHaveNoViolations} from 'jest-axe'
  +import 'babel-polyfill'
  +expect.extend(toHaveNoViolations)
  describe('Caret', () => {
  it('renders <svg>', () => {
  expect(render(<Caret />).type).toEqual('svg')
  })
  + it("should have no axe violations", async () => {
  + const {container} = HTMLRender(<Caret/>)
  + const results = await axe(container)
  + expect(results).toHaveNoViolations()
  + cleanup()
  + })
  +
  it('renders cardinal directions', () => {
  for (const location of ['top', 'right', 'bottom', 'left']) {
  expect(render(<Caret location={location} theme={theme} />)).toMatchSnapshot()
  