testing-patterns

grmkris's avatarfrom grmkris

Test infrastructure patterns - PGlite for in-memory PostgreSQL, Redis/S3 mocks, TestSetup factory, Vitest. Use when writing tests or adding test infrastructure.

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[Testing and QA]

When & Why to Use This Skill

This Claude skill provides standardized testing infrastructure patterns for modern TypeScript applications, leveraging PGlite for in-memory PostgreSQL, Redis/S3 mocks, and the Vitest framework. It streamlines the creation of isolated, high-performance test environments through a centralized TestSetup factory, ensuring consistent, reliable, and fast automated testing cycles.

Use Cases

  • Setting up fast, isolated database tests using PGlite to eliminate the need for external PostgreSQL instances during CI/CD.
  • Mocking cloud-native services like Redis and S3 to test infrastructure-dependent logic locally without incurring costs or latency.
  • Implementing a standardized TestSetup factory pattern to manage complex dependency injection and lifecycle hooks across a monorepo.
  • Accelerating the development of server-side integration tests with pre-configured Vitest templates and utility helpers for user authentication and data seeding.
nametesting-patterns
descriptionTest infrastructure patterns - PGlite for in-memory PostgreSQL, Redis/S3 mocks, TestSetup factory, Vitest. Use when writing tests or adding test infrastructure.

Testing Infrastructure

Use this skill when writing tests. Tests use isolated in-memory infrastructure.

Project Setup

Replace these placeholders for your project:

  • @project/ → your package scope (e.g., @myapp/)
  • packages/ paths follow standard monorepo layout

Expected packages:

  • @project/test-utils - In-memory infrastructure (PGlite, Redis, S3)
  • @project/shared/typeid - TypeID validators

Test File Location

  • Server tests: apps/server/test/**/*.test.ts
  • Use Vitest (describe, it, expect, beforeAll, afterAll)

Quick Start Template

import { describe, it, expect, beforeAll, afterAll } from "vitest";
import { type TestSetup, createTestSetup } from "../test/test.setup";
import { createTestContext, createTestItem, fundUser } from "../test/test-helpers";
import { UserId } from "@project/shared/typeid";

describe("Feature Name", () => {
  let testSetup: TestSetup;

  beforeAll(async () => {
    testSetup = await createTestSetup();
  });

  afterAll(async () => {
    await testSetup.cleanup();
    await testSetup.close();
  });

  it("should do something", async () => {
    const { deps, users } = testSetup;
    const userId = UserId.parse(users.authenticated.id);

    const item = await createTestItem(deps.db, { title: "Test Item" });
    await fundUser(deps.userService, userId, 100);

    const result = await deps.itemService.create(userId, {
      itemId: item.id,
      value: "test",
    });

    expect(result.isOk()).toBe(true);
  });
});

Additional Resources

  • For TestSetup structure and in-memory infra, see setup.md
  • For test helper functions, see helpers.md