title: How to get a code coverage report with react-create-app?
body: <p>If I run</p>
  <pre><code>npm test --coverage
  </code></pre>
  <p>the tests pass, but the coverage is not run.</p>
  <p>When I change <code>package.json</code> to have</p>
  <pre><code>react-scripts test --coverage
  </code></pre>
  <p>Then, when I do <code>npm test</code> and <code>a</code> it runs the tests but not the coverage</p>
  <p>The tests run along with the coverage report but the coverage shows all zeroes for coverage</p>
  <pre><code> PASS  src/components/Header/SubHeader.test.js
    The &lt;SubHeader /&gt; component
      ✓ should render (4ms)
      ✓ should render with a goback button (1ms)
      ✓ should render
  
  ----------|----------|----------|----------|----------|-------------------|
  File      |  % Stmts | % Branch |  % Funcs |  % Lines | Uncovered Line #s |
  ----------|----------|----------|----------|----------|-------------------|
  All files |        0 |        0 |        0 |        0 |                   |
  ----------|----------|----------|----------|----------|-------------------|
  Test Suites: 1 passed, 1 total
  Tests:       3 passed, 3 total
  Snapshots:   3 passed, 3 total
  Time:        1.077s
  Ran all test suites.
  </code></pre>
  <p>Finally, I realized that I can do</p>
  <pre><code>npm run test .
  </code></pre>
  <p>Question: Why don't the other methods work?</p>