I have a usage-based Stripe product for which an invoice is generated at the end of the billing period (month). I am trying to use a Test Clock to verify that the usage is recorded on the invoice.

I am adding the usage to the invoice while it is in draft mode by listening for the invoice.created webhook, calculating the usage, and reporting it to the meter with a timestamp within the billing period for the invoice (see the docs). However, the Invoice in the Subscription never sees the usage I submit.

Restated in more detail, I follow these steps in Test Mode:

1. Create a Test Clock
2. Create a Customer in the Test Clock
3. Create a monthly Subscription in the Test Clock for the newly created Customer which starts at the current time
4. Advance the Test Clock one month, which triggers the invoice.created event on the webhook.
5. My code in the webhook runs to record the usage:

const invoice = event.data.object;
const {
  id,
  customer: stripeCustomerId,
  customer_email: email,
  period_start: invoicePeriodStart,
  period_end: invoicePeriodEnd,
  subscription: stripeSubscriptionId,
  status,
} = invoice;

try {
  // A finalized invoice is created when the user first signs up for the usage-based subscription; we want to ignore this one
  if (status !== 'draft') return;

  // Manually created invoices do not have a subscription and are not of interest for our purposes here
  if (!stripeSubscriptionId) return;

  // Only report usage for invoices that are for the usage-based subscription
  const subscription = await stripe.subscriptions.retrieve(stripeSubscriptionId);
  if (subscription.items.data[0].price.lookup_key !== myLookupKey) {
    console.log(
      `Subscription lookup key ${subscription.items.data[0].price.lookup_key} !== ${myLookupKey}`,
    );
    return;
  }

  const user = await users.findByEmail(email);

  // Call another server to get the usage for the previous period 
  const organization = useranization;
  const startDate = new Date(invoicePeriodStart * 1000);
  const endDate = new Date(invoicePeriodEnd * 1000);
  const usageString = await crossServerPostRequest(
    new URL(`<URL FOR GETTING USAGE FOR PERIOD>`),
    {
      organization,
      startDate,
      endDate,
    },
  );

  await stripe.billing.meterEvents.create({
    event_name: 'event_name',
    identifier: crypto.randomUUID(),
    payload: {
      value: parseInt(usageString, 10),
      stripe_customer_id: stripeCustomerId,
    },
    timestamp: invoicePeriodEnd, invoicePeriodStart + (invoicePeriodEnd - invoicePeriodStart) / 2, // I've tried a few different values here: invoicePeriodStart, invoicePeriodEnd
  });

  postSlackMessage(
      `Usage reported to Stripe for ${useranization}: ${usageString} (${startDate.toDateString()} - ${endDate.toDateString()})`,
    );
} catch (error) {
  console.error(error);
  postSlackMessage(
    `Error during invoice.created Stripe webhook for ${id} for ${request.body.email}; usage may not have been reported\n${error}`,
  );
}

6. I observe the event on the Stripe Dashboard for the Meter and it is associated with my Test Clock customer
7. I advance the Test Clock another hour so that the invoice will finalize
8. I observe the finalized invoice and it does not include the usage

Am I doing something wrong? Do Test Clocks not work with Meters like this? Nothing is noted about Meters in the Stripe docs Test Clock Limitations.

I also tried advancing the test clock to the middle of the period, putting in a Meter Event manually on the Stripe Dashboard for the Test Clock customer, and advancing the test clock to the end and I did not see the usage in that instance either.

I got this to work a few times with the Meter Event timestamp set to invoicePeriodStart, but not consistently. I know Meter events are processed asynchronously - maybe this is causing inconsistent results? I want to be confident my process will work in live mode.