message: simplify UnderlineNavLink tests
diff: import React from 'react'
  +import {ITEM_CLASS} from '../UnderlineNav'
  import UnderlineNavLink from '../UnderlineNavLink'
  import {render} from '../utils/testing'
  @@ -10,7 +11,7 @@ describe('Caret', () => {
  it('renders the given tag prop', () => {
  const Type = props => <b {...props} />
  expect(render(<UnderlineNavLink tag={Type} />)).toEqual(
  - render(<b className="UnderlineNav-item no-underline px-3" activeClassName="selected" />)
  + render(<b className={ITEM_CLASS} />)
  )
  })
  })
  