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zulip/docs/subsystems/billing.md

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Billing (Development)

This section deals with developing and testing the billing system.

Common setup

  • Create a Stripe account
    • Make sure that the country of your Stripe account is set to USA when you create the account.
    • You might need to use a VPN for this.
  • Ensure that the API version of your Stripe account is same as STRIPE_API_VERSION defined in corporate/lib/stripe.py. You can upgrade to a higher version from the Stripe dashboard.
  • Set the private API key.
    • Go to https://dashboard.stripe.com/test/apikeys
    • Double-check that you're viewing test API keys (not live keys) to avoid actual charges while testing code.
    • Add stripe_secret_key to zproject/dev-secrets.conf.

Manual testing

Manual testing involves testing the various flows like upgrade, card change, etc. through the browser. This is the bare minimum testing that you need to do when you review a billing PR or when you are working on adding a new feature to billing.

Setup

Apart from the common setup mentioned above, you also need to set up your development environment to receive webhook events from Stripe.

  • Install the Stripe CLI locally by following the instructions here.
  • Log in to Stripe CLI using the command stripe login.
  • You can get Stripe CLI to forward all Stripe webhook events to our local webhook endpoint using the following command: stripe listen --forward-to http://localhost:9991/stripe/webhook/
  • Note that the webhook secret key needs to be updated every 90 days following the steps here.
  • Wait for the stripe listen command in the previous step to output the webhook signing secret.
    • The signing secret would be used by our billing system to verify that the events received by our webhook endpoint are sent by Stripe and not by an intruder. In production, there is no Stripe CLI, so the step for configuring this is a bit different. See Stripe's documentation on taking webhooks live for more details.
  • Copy the webhook signing secret and set it as stripe_webhook_endpoint_secret in zproject/dev-secrets.conf.
  • Your development environment is now all set to receive webhook events from Stripe.
  • With tools/run-dev stopped, you can run ./manage.py populate_billing_realms to populate different billing states, both Cloud and Self-hosted, with various initial plans and billing schedules.
  • Feel free to modify populate_billing_realms to add more states if they seem useful in your testing. After running the command, you will see a list of populated organizations.
  • Populated Cloud-style Realms can be accessed as follows:
    • Logout and go to localhost:9991/devlogin.
    • Select the realm from the Realms dropdown you wist to test.
    • Login as the only available user.
    • Go to /billing.
  • Populated RemoteZulipServer customers can be accessed by going to http://selfhosting.localhost:9991/serverlogin/ and providing the credentials in the login form for the server state you wish to test. The credentials are printed in the terminal by ./manage.py populate_billing_realms.
  • Populated RemoteRealm customers can be accessed simply by follow their links printed in the terminal in the ./manage.py populate_billing_realms output.

Test card numbers

Stripe provides various card numbers to test for specific responses from Stripe. The most commonly used ones are mentioned in below wherever appropriate. The full list is available here.

Flows to test

There are various flows that you can test manually from the browser. Here are a few things to keep in mind while conducting these tests manually:

  • The flows work from start to end as expected.
  • We show appropriate success and error messages to users.
  • Charges are made or not made (free trial) as expected. You can verify this through the Stripe dashboard. However, this is not super important since our automated tests take care of such granular testing for us.
  • Renewals can be tested by calling ./manage.py invoice_plans --date 2024-04-30T08:12:53 -- this will run invoicing, including end-of-cycle updates, as though the current date is as specified.

Upgrading a Zulip Cloud organization

Here are some flows to test when upgrading a Zulip Cloud organization:

  • When free trials are not enabled, i.e. CLOUD_FREE_TRIAL_DAYS is not set to any value in dev_settings.py (aka the default). You can double-check that the setting is disabled by verifying ./scripts/get-django-setting CLOUD_FREE_TRIAL_DAYS returns 0.

    • Using a valid card number like 4242 4242 4242 4242, the official Visa example credit card number.
    • Using an invalid card number like 4000000000000341, which will add the card to the customer account but the charge will fail.
      • Retry the upgrade after adding a new card by clicking on the retry upgrade link.
      • Retry the upgrade from scratch.

  • Upgrade an organization when free trials are enabled. The free trials setting has been (possibly permanently) disabled in production for some time now, so testing this code path is not a priority. You can set CLOUD_FREE_TRIAL_DAYS to any number greater than 0 in dev_settings.py to enable free trials. There are two different flows to test here:

    • Right after the organization is created by following the instructions in the onboarding page.
      • Make sure that after the upgrade is complete the billing page shows a link to go to the organization.
    • By manually going to the /billing page and upgrading the organization.

Upgrading a remote Zulip organization

Here are some flows to test when upgrading a remote Zulip organization:

  • Free trial for remote organizations is enabled by default by setting SELF_HOSTING_FREE_TRIAL_DAYS to 30 days. You can change this value and other settings for your development environment only in zproject/custom_dev_settings.py, or secrets in zproject/dev-secrets.conf. Note that this only provides free trail for the basic plan.

    • Using a valid card number like 4242 4242 4242 4242, the official Visa example credit card number.
    • Using an invalid card number like 4000000000000341, which will add the card to the customer account but the charge will fail.
      • Retry the upgrade after adding a new card by clicking on the retry upgrade link.
      • Retry the upgrade from scratch.

  • Try upgrading to Zulip Business using Pay by card as described above or Pay by Invoice.

Changing the card

The following flow should be tested when updating cards in our billing system:

  • Go to the /billing page of an organization that has already been upgraded using a card. Try changing the card to another valid card such as 5555555555554444.
    • Make sure that the flow completes without any errors and that the new card details are now shown on the billing page instead of the older card.
  • You can also try adding a card number that results in it getting attached to the customer's account but charges fail. However, to test this, you need pending invoices since we try to charge for pending invoices when the card is updated. This is tested in our automated tests so it is not strictly necessary to test this manually.

Upgrading Stripe API versions

Stripe makes pretty regular updates to their API. The process for upgrading our code is:

  • Go to the Stripe Dashboard in your Stripe account.
  • Upgrade the API version.
  • Run tools/test-backend --generate-stripe-fixtures --parallel=1 corporate/.
  • Fix any failing tests, and manually look through git diff to understand the changes. Ensure that there are no material changes.
  • Update the value of STRIPE_API_VERSION in corporate/lib/stripe.py.
  • Commit the changes, and open a PR.
  • Ask Tim Abbott to upgrade the API version on the Stripe Dashboard for Zulip's official Stripe account.

We currently aren't set up to do version upgrades where there are breaking changes, though breaking changes should be unlikely given the parts of the product we use. The main remaining work for handling breaking version upgrades is ensuring that we set the stripe version in our API calls. Stripe's documentation for Upgrading your API version has some additional information.

Writing tests

Writing new tests is fairly easy. Most of the tests are placed in test_stripe. If you need do API calls to stripe, wrap the test function in @mock_stripe and run tools/test-backend TEST_NAME --generate-stripe-fixtures. It will run all your calls and generate fixtures for any API calls to stripe, so that they can be used to consistently run that test offline. You can then commit the new test fixtures along with your code changes.

Regenerating the fixtures for all of our existing billing tests is expensive, in that it creates extremely large diffs from editing dates/IDs that grow the zulip/zulip Git repository and make PRs harder to read, both visually and by making the GitHub UI very slow.

So you should generally aim to only (re)generate fixtures where it's necessary, such as when we change how we're calling some Stripe APIs or adding new tests.

So you'll usually want to pass --generate-stripe-fixtures only when running the tests for a specific set of tests whose behavior you know that you changed. Once you've committed those changes, you can verify that everything would pass if new fixtures were generated as follows:

  • Run tools/test-backend corporate/ --generate-stripe-fixtures.
  • If it passes, you can just run git reset --hard to drop the unnecessary fixture updates.
  • If it fails, you can do the same, but then rerun the tests that failed with --generate-stripe-fixtures as you debug them.
  • In either case, you can skip the diffs for any unexpected changes in payloads before dropping them, though it's pretty painful to do so given how many files have IDs change.