Issue when running tests with --watchAll=false --coverage

Describe the bug

When I attempt to run my tests with coverage in CI (or locally for that matter) I get an error: App(...): Nothing was returned from render. This usually means a return statement is missing. Or, to render nothing, return null.

Did you try recovering your dependencies?

N/A (happens on a fresh bootstrap of a new app

Which terms did you search for in User Guide?

N/A, though I did search for the error in the issues and found nothing

Environment

Environment Info:

  current version of create-react-app: 3.4.1
  running from /Users/kentcdodds/.npm/_npx/59115/lib/node_modules/create-react-app

  System:
    OS: macOS 10.15.3
    CPU: (16) x64 Intel(R) Core(TM) i9-9980HK CPU @ 2.40GHz
  Binaries:
    Node: 12.13.1 - ~/n/bin/node
    Yarn: 1.21.1 - ~/.yarn/bin/yarn
    npm: 6.14.3 - /usr/local/bin/npm
  Browsers:
    Chrome: 80.0.3987.149
    Firefox: 71.0
    Safari: 13.0.5
  npmPackages:
    react: ^16.13.1 => 16.13.1 
    react-dom: ^16.13.1 => 16.13.1 
    react-scripts: 3.4.1 => 3.4.1 
  npmGlobalPackages:
    create-react-app: Not Found

Steps to reproduce

Reproduction steps:

npm create react-app coverage-issues
cd coverage-issues
npx react-scripts test --watchAll=false --coverage

Expected behavior

I expect the test to pass and coverage to be reported

Actual behavior

Here’s the relevant output:

 FAIL  src/App.test.js
  ✕ renders learn react link (22ms)

  ● renders learn react link

    App(...): Nothing was returned from render. This usually means a return statement is missing. Or, to render nothing, return null.

      4 | 
      5 | test('renders learn react link', () => {
    > 6 |   const { getByText } = render(<App />);
        |                         ^
      7 |   const linkElement = getByText(/learn react/i);
      8 |   expect(linkElement).toBeInTheDocument();
      9 | });

      at reconcileChildFibers (node_modules/react-dom/cjs/react-dom.development.js:14348:23)
      at reconcileChildren (node_modules/react-dom/cjs/react-dom.development.js:16762:28)
      at mountIndeterminateComponent (node_modules/react-dom/cjs/react-dom.development.js:17542:5)
      at beginWork (node_modules/react-dom/cjs/react-dom.development.js:18596:16)
      at HTMLUnknownElement.callCallback (node_modules/react-dom/cjs/react-dom.development.js:188:14)
      at Object.invokeGuardedCallbackDev (node_modules/react-dom/cjs/react-dom.development.js:237:16)
      at invokeGuardedCallback (node_modules/react-dom/cjs/react-dom.development.js:292:31)
      at beginWork$1 (node_modules/react-dom/cjs/react-dom.development.js:23203:7)
      at performUnitOfWork (node_modules/react-dom/cjs/react-dom.development.js:22157:12)
      at workLoopSync (node_modules/react-dom/cjs/react-dom.development.js:22130:22)
      at performSyncWorkOnRoot (node_modules/react-dom/cjs/react-dom.development.js:21756:9)
      at scheduleUpdateOnFiber (node_modules/react-dom/cjs/react-dom.development.js:21188:7)
      at updateContainer (node_modules/react-dom/cjs/react-dom.development.js:24373:3)
      at node_modules/react-dom/cjs/react-dom.development.js:24758:7
      at unbatchedUpdates (node_modules/react-dom/cjs/react-dom.development.js:21903:12)
      at legacyRenderSubtreeIntoContainer (node_modules/react-dom/cjs/react-dom.development.js:24757:5)
      at Object.render (node_modules/react-dom/cjs/react-dom.development.js:24840:10)
      at node_modules/@testing-library/react/dist/pure.js:86:25
      at batchedUpdates$1 (node_modules/react-dom/cjs/react-dom.development.js:21856:12)
      at act (node_modules/react-dom/cjs/react-dom-test-utils.development.js:929:14)
      at render (node_modules/@testing-library/react/dist/pure.js:82:26)
      at Object.<anonymous> (src/App.test.js:6:25)

Reproducible demo

The reproduction steps should be enough. You don’t need to change anything about the generated project.

I am also experiencing this in all of my react-scripts apps. I think this only started happening in the last week or so.

[sarahatwork]

Ran into this issue today. Downgraded to react-scripts 3.4.0 in my package.json as a workaround.

[wescopeland]

One thing I noticed is that if you remove --watchAll=false or --coverage then this is not an issue. It’s only a problem if you have both of those together.

We are experiencing this with the --coverage flag, even if --watchAll=false is removed.