test coverage is empty - v3.0.0

Created by: pete-redmond-cko

Is this a bug report?

yes, test coverage is always empty

After updating react-scripts to 3.0.0 test coverage is always empty, this worked before in v2.1.8

v2.1.8

v3.0.0

Did you try recovering your dependencies?

This happens after booting an app up using create react app using typescript create-react-app cra-coverage-example --typescript

Which terms did you search for in User Guide?

n/a

Environment

Environment Info:

  System:
    OS: macOS 10.14.4
    CPU: x64 Intel(R) Core(TM) i5-7360U CPU @ 2.30GHz
  Binaries:
    Node: 11.12.0 - ~/.nvm/versions/node/v11.12.0/bin/node
    Yarn: 1.15.2 - /usr/local/bin/yarn
    npm: 6.7.0 - ~/.nvm/versions/node/v11.12.0/bin/npm
  Browsers:
    Chrome: 73.0.3683.103
    Safari: 12.1
  npmPackages:
    react: ^16.8.6 => 16.8.6
    react-dom: ^16.8.6 => 16.8.6
    react-scripts: 3.0.0 => 3.0.0
  npmGlobalPackages:
    create-react-app: Not Found

Steps to Reproduce

create-react-app cra-coverage-example --typescript
yarn test --coverage

Expected Behavior

test coverage would be output

Actual Behavior

test coverage is always empty

Reproducible Demo

https://github.com/pete-redmond-cko/cra-coverage-example or you can spin up an app using create react app v.3.0.0 and run yarn test --coverage