component.js

/* @flow */

import React from 'react'
import messages from '../messages'
import { injectIntl } from 'react-intl'
import type { IntlShape } from 'react-intl'

type Props = {|
  children: React.Node,
  intl: IntlShape,
|}

export class Foo extends React.Component<Props> {
  render() {
    const { formatMessage } = this.props.intl
    
    return (
      <React.Fragment>
        <h1>{formatMessage(messages.something)}</h1>
        {this.props.children}
      </React.Fragment>           
    )
  }
}

export default injectIntl(Foo)

intl-test-helper.js

/* @flow */

import { IntlProvider } from 'react-intl'
import type { IntlShape } from 'react-intl'
const intlProvider = new IntlProvider({ locale: 'en' }, {})

export const intl: IntlShape = intlProvider.getChildContext().intl
export const intlWrapped = (name: string): string => `InjectIntl(${name})`