Babel error when running tests with --coverage

Created by: gaelollivier

Description

Steps:

• create a fresh app
• anywhere inside App.js, add the following code

function* test() {
  yield ((a) => 42)
}

• run npm run test => works
• run npm run test -- --coverage => crashes

Expected behavior

This syntax is valid js, it works in the browser and with tests without coverage so I expect it to work with coverage activated

Actual behavior

This error is thrown:

Environment

1. npm ls react-scripts

test@0.1.0 /Users/gael/Desktop/test
└── react-scripts@0.8.1

2. node -v:

v6.4.0

3. npm -v:

3.10.6

1. Operating system: OSX 10.12.1
2. Browser and version: N/A

I guess this is a Jest issue, so I ping @cpojer ?