One test!
If you don't have any tests, anything is already better than nothing.
So start with one test.
Check out and choose which one you prefer:
And then start testing one component, one process, one "happy path".
How to use this
I used pnpm here, so you need to have pnpm installed globally.
pnpm install
# unit tests
pnpm test
# e2e tests
pnpm test:cyOutro
Happy testing!