How do I test what happens when a subscription renews without waiting a month

Test clocks. They're made for exactly this.

1. Create a test clock (Dashboard > Billing > Test clocks, or stripe.testHelpers.testClocks.create({ frozen_time })).
2. Create a customer attached to the clock (test_clock: clock.id) and a subscription for them with your real monthly price.
3. Advance the clock by a month. Stripe generates the renewal invoice, attempts payment, and fires invoice.created, invoice.paid, customer.subscription.updated, same as in real life.

Use the 4000 0000 0000 0341 test card (attaches fine, fails on charge) to test the failed renewal path too.

One gotcha: when you advance, events arrive in a burst. If your handler assumes order, you'll find out here, which is a good thing.