useEffect not triggering inside jest

• react-testing-library version: 5.2.3
• react version: 16.7.0-alpha.0
• node version: CodeSandbox
• npm (or yarn) version: CodeSandbox

Relevant code or config:

  let a = false;
  function Test() {
    React.useEffect(() => {
      a = true;
    });
    return <div>Hello World</div>;
  }
  render(<Test />);
  expect(a).toBe(true);

What you did:

I’m trying to test functions with the useEffect hook inside jest.

What happened:

The useEffect hook is not executed correctly inside a jest environment after calling render(<Test />). However it appears to be working correctly if it is called directly in a browser environment.

Reproduction:

Working example: https://codesandbox.io/s/l947z8v6xq (index.js) Not working example in jest: https://codesandbox.io/s/7k5oj92740 (index.test.js)

Problem description:

The useEffect hook should have been executed after the render call