message: update SubNav tests
diff: @@ -2,6 +2,10 @@ import React from 'react'
  import SubNav from '../SubNav'
  import {mount, render, rendersClass} from '../utils/testing'
  import {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('SubNav', () => {
  it('implements system props', () => {
  @@ -12,6 +16,13 @@ describe('SubNav', () => {
  expect(SubNav).toSetDefaultTheme()
  })
  + it('should have no axe violations', async () => {
  + const {container} = HTMLRender(<SubNav />)
  + const results = await axe(container)
  + expect(results).toHaveNoViolations()
  + cleanup()
  + })
  +
  it('renders a <nav>', () => {
  expect(render(<SubNav />).type).toEqual('nav')
  })
  