message: add pilot test for computed responsive styles
diff: import React from 'react'
  import Block from '../Block'
  import theme from '../theme'
  -import {render} from '../utils/testing'
  +import {mount, render} from '../utils/testing'
  import {COMMON, LAYOUT} from '../system-props'
  +const {breakpoints, space} = theme
  +
  describe('Block', () => {
  + it('renders styles', () => {
  + expect(<Block m={[0, 1, 2]} />).toRenderStyles({
  + margin: '0px',
  + [`@media screen and (min-width:${breakpoints[0]})`]: {
  + margin: `${space[1]}px`
  + },
  + [`@media screen and (min-width:${breakpoints[1]})`]: {
  + margin: `${space[2]}px`
  + }
  + })
  + })
  +
  it('is a system component', () => {
  expect(Block.systemComponent).toEqual(true)
  })
  