You know that you need to write tests for your components. It's not that you don't want to write the actual tests; it's that setting them up so that they're able to run can be a pain. The Jest unit test tool simplifies this because it knows where tests can be found and can run them:
With Jest, we have a place where all of our unit tests go, and each depend on the component that they're testing. This tool knows where to find these tests and how to run them. The result is that we get nice unit test and code coverage output when we need it. There is no overhead beyond actually writing the tests.