message: add renderWithTheme() test helper
diff: +import React from 'react'
  import renderer from 'react-test-renderer'
  import enzyme from 'enzyme'
  import Adapter from 'enzyme-adapter-react-16'
  +import {ThemeProvider} from 'emotion-theming'
  +import {default as defaultTheme} from '../theme'
  enzyme.configure({adapter: new Adapter()})
  @@ -42,3 +45,9 @@ export function renderClasses(component) {
  export function rendersClass(node, klass) {
  return renderClasses(node).includes(klass)
  }
  +
  +export function renderWithTheme(node, theme = defaultTheme) {
  + return render(
  + <ThemeProvider theme={theme}>{node}</ThemeProvider>
  + )
  +}
  