How can I configure jest to handle SvelteKit's `$lib` alias?

Question

When I try to run a test in jest that imports a file using the $lib alias, jest fails to run with the error Cannot find module '$lib/...'.

user_5955911 · Answer

Add the following to jest.config.cjs:

module.exports = {
  ...,
  moduleNameMapper: { '^\$lib(.*)$': '/src/lib$1' },
}

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