Test Factories

Factories create realistic test data with sensible defaults, reducing boilerplate in tests.

Pattern

Each factory is a function that accepts partial overrides and returns a complete object. Integration tests use factories with the real database; unit tests use them as plain objects.

Example Template

typescript

// tests/factories/user.factory.ts
import { db } from "@/lib/db";
import { users } from "@/lib/db/schema";

let counter = 0;

function uniqueEmail() {
  return `user-${++counter}-${Date.now()}@example.com`;
}

export function buildUser(overrides: Partial<typeof users.$inferInsert> = {}) {
  return {
    id: crypto.randomUUID(),
    email: uniqueEmail(),
    name: "Test User",
    createdAt: new Date(),
    ...overrides,
  };
}

/** Insert a user into the real DB and return the row. */
export async function createUser(overrides: Partial<typeof users.$inferInsert> = {}) {
  const [row] = await db.insert(users).values(buildUser(overrides)).returning();
  return row;
}

Usage in Unit Tests

typescript

import { buildUser } from "../factories/user.factory";

test("formats display name", () => {
  const user = buildUser({ name: "Jane Doe" });
  expect(formatDisplayName(user)).toBe("Jane Doe");
});

Usage in Integration Tests

typescript

// tests/integration/users.test.ts
import { createUser } from "../factories/user.factory";

test("GET /api/users/:id returns the user", async () => {
  const user = await createUser({ name: "Integration User" });
  const res = await fetch(`http://localhost:3015/api/users/${user.id}`);
  expect(res.status).toBe(200);
  const body = await res.json();
  expect(body.name).toBe("Integration User");
});

Rules

build* functions return plain objects — no DB calls, safe for unit tests.
create* functions insert into the real DB — use only in integration tests.
Always clean up after integration tests (use afterEach with db.delete(...) or run tests in transactions that roll back).
Use counters or timestamps to ensure unique values across parallel test runs.