RTL error: not wrapped in act()

[lorensr]

How to fix this?

git checkout 28
npm test

src/components/App.test.js

import React from 'react'
import App from './App'

it('renders without crashing', () => {
 mockedRender(<App />)
})

has a number of errors like this:

 console.error node_modules/react-dom/cjs/react-dom.development.js:88
 Warning: An update to _default inside a test was not wrapped in act(...).
 
 When testing, code that causes React state updates should be wrapped into act(...):
 
 act(() => {
 /* fire events that update state */
 });
 /* assert on the output */
 
 This ensures that you're testing the behavior the user would see in the browser. Learn more at https://fb.me/react-wrap-tests-with-act
 in _default (at App.js:61)
 in header (at App.js:55)
 in div (at App.js:54)
 in _default (at App.test.js:5)
 in ApolloProvider
 in Unknown (at setupTests.js:47)
 in Router (at setupTests.js:36)
 in RouterWrapper (at setupTests.js:46)
 in MockedWrapper