feat: add web testing foundation with infra-backed suites (#349)

* feat: add web test framework with infra-backed suites

* fix: honor DATABASE_URL env in integration prepare script

* fix: apply web test review feedback

* fix: streamline web test infra lifecycle and workflow scope

apps/web/src/lib/usage.ts

@@ -54,9 +54,9 @@ export function getUsageDate(): string {
  * @param transactionUsage Number of transaction emails sent
  * @returns Total usage units rounded down to nearest integer
  */
-export function getUsageUinits(
+export function getUsageUnits(
   marketingUsage: number,
-  transactionUsage: number
+  transactionUsage: number,
 ) {
   return (
     marketingUsage +

apps/web/src/lib/usage.unit.test.ts

@@ -0,0 +1,35 @@
+import { EmailUsageType } from "@prisma/client";
+import { afterEach, describe, expect, it, vi } from "vitest";
+import {
+  getCost,
+  getUsageDate,
+  getUsageTimestamp,
+  getUsageUnits,
+  TRANSACTIONAL_UNIT_CONVERSION,
+} from "~/lib/usage";
+
+describe("usage helpers", () => {
+  afterEach(() => {
+    vi.useRealTimers();
+  });
+
+  it("returns yesterday date and timestamp", () => {
+    vi.useFakeTimers();
+    vi.setSystemTime(new Date("2026-02-08T12:00:00.000Z"));
+
+    expect(getUsageDate()).toBe("2026-02-07");
+    expect(getUsageTimestamp()).toBe(
+      Math.floor(new Date("2026-02-07T12:00:00.000Z").getTime() / 1000),
+    );
+  });
+
+  it("converts transactional usage into billing units", () => {
+    const units = getUsageUnits(100, 40);
+    expect(units).toBe(100 + Math.floor(40 / TRANSACTIONAL_UNIT_CONVERSION));
+  });
+
+  it("calculates cost per email type", () => {
+    expect(getCost(10, EmailUsageType.MARKETING)).toBe(0.01);
+    expect(getCost(4, EmailUsageType.TRANSACTIONAL)).toBe(0.001);
+  });
+});