write-test

What I do

Write integration tests for the Autumn billing system using the initScenario pattern.

Before Writing Any Test

ALWAYS read these codebase files FIRST: 1. server/tests/TEST_GUIDE.md - Core patterns, fixtures, scenario builder 2. For billing tests: server/tests/integration/billing/update-subscription/BILLING_GUIDE.md

Critical Rules

DO: - Use test.concurrent() for isolated, parallel tests - Use initScenario with s.* builders - Use product.id in s.attach() (never string literals) - Use Decimal.js for balance calculations in track tests - Unique customerId per test

DON'T: - Use describe/beforeAll/test (legacy pattern) - Use Date.now() with test clocks (use advancedTo) - Share state between tests - Use raw arithmetic for balance calculations (floating point errors)

Minimal Template

import { expect, test } from "bun:test";
import { type ApiCustomerV3 } from "@autumn/shared";
import { expectCustomerFeatureCorrect } from "@tests/integration/billing/utils/expectCustomerFeatureCorrect";
import { TestFeature } from "@tests/setup/v2Features.js";
import { items } from "@tests/utils/fixtures/items.js";
import { products } from "@tests/utils/fixtures/products.js";
import { initScenario, s } from "@tests/utils/testInitUtils/initScenario.js";
import chalk from "chalk";

test.concurrent(`${chalk.yellowBright("feature: description")}`, async () => {
  const messagesItem = items.monthlyMessages({ includedUsage: 100 });
  const pro = products.base({ id: "pro", items: [messagesItem] });

  const { customerId, autumnV1 } = await initScenario({
    customerId: "unique-test-id",
    setup: [s.customer({ paymentMethod: "success" }), s.products({ list: [pro] })],
    actions: [s.attach({ productId: pro.id })],
  });

  const customer = await autumnV1.customers.get<ApiCustomerV3>(customerId);
  expectCustomerFeatureCorrect({ customer, featureId: TestFeature.Messages, balance: 100 });
});

References

Load these on-demand for detailed information:

• references/SCENARIO.md - Scenario initialization, product configs, s.* builders
• references/FIXTURES.md - Item and product fixtures with all params
• references/ENTITIES.md - Entity-based testing (multi-tenant, per-entity billing)
• references/TRACK-CHECK.md - Track/check endpoint testing, credit systems, Decimal.js
• references/EXPECTATIONS.md - All expectation utilities
• references/GOTCHAS.md - Common pitfalls, debugging, billing edge cases

File Location

Tests: server/tests/integration/billing/ organized by feature area.

Run Tests

bun test path/to/file.test.ts