What's up with webhooks?
Webhooks are used extensively at Stripe and are a great way to make sure your database is up to date with Stripe. They take care, amongst other things, to let you know a trial is over (first charge of their credit card), a subscription is renewed or a charge has failed (after Stripe’s retried)—thus the subscription should be canceled.
To test webhooks locally you can use a service like ngrok.com. Though Stripe also provides a CLI to work with their webhooks (amongst other things).