Add Debug Jest Tests In create-react-app as a react til

react/debug-jest-tests-in-create-react-app.md

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+# Debug Jest Tests In create-react-app
+
+When you put a `debugger;` statement in one of your Jest tests and
+run `yarn test`, the test runner will ignore the debug statement and run to
+completion. This is because Jest defaults to parallelizing tests which won't
+mix well with manual debugging intervention.
+
+If we want to be able to run our Jest tests through a debugger. We will need
+two things. First, we need a debugging environment -- Chrome's devtools will
+work well for this. Second, we need our tests to run in band. The
+[`react-scripts`
+documentation](https://github.com/facebook/create-react-app/blob/master/packages/react-scripts/template/README.md#debugging-tests)
+recommends adding a second, debug-specific test command to your
+`package.json`:
+
+```javascript
+"scripts": {
+  "test:debug": "react-scripts --inspect-brk test --runInBand --env=jsdom"
+}
+```
+
+You can now run `yarn test:debug` which will start a paused debug session.
+Open chrome at `chrome://inspect` to access and open the debugging session
+panel. Now, debug away.