Misc

Jest is a javascript unit testing framework
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Running only subsets of tests

Because I edited my package.json like this…

"scripts": {
    "test": "jest",
    "test:char": "jest --watchAll --testPathPattern=src/character-copier",
    "test:fizzbuzz": "jest --watchAll --testPathPattern=src/fizzbuzz"
  },

… I can run this in the terminal - npm run test:char - and it will watch my code and run tests in the background, but only for the specified folder.

Troubleshooting with React

Invalid hook

When you get an error saying invalid hook in jest tests:
you might need to update your version of jest
- like this: npm install react-router-dom@6
https://reactjs.org/link/invalid-hook-call
https://github.com/next-page-tester/next-page-tester/issues/147

testing-library issues

“Cannot find module ‘@testing-library/react’ from [path to test file]”

Solution: npm install --save-dev @testing-library/react
or npm install --save @testing-library/react @testing-library/jest-dom

Can’t install testing library because dependencies

ERESOLVE unable to resolve dependency tree npm ERR! npm ERR! While resolving: client@0.1.0 npm ERR! Found: react@17.0.2 npm ERR! node_modules/react npm ERR! react@”^17.0.2” from the root project

This is because you have an old version of react

Solution: npm install react react-dom to get latest version

Upgrading react has no impact

package.json still has "react": "^17.0.2", even after running npm install react react-dom

Solution:

Run the install command in the ROOT of your project (one level higher than client and server)
Remove the older react and react-dom versions from dependencies in package.son in the sub-project
Run npm install again (in the sub-folder)

Jest

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