The project uses jest library for tests. (see "test" script in package.json) There is 1 test (server.test.js) in the project that checks whether the main index.html file exists in the project.
To run the nodejs test:
npm run test
Make sure to download jest library before running test, otherwise jest command defined in package.json won't be found.
npm install
In order to see failing test, remove index.html or rename it and run tests.