Knowledge Index — 지식 지도

Tests that inspect internal component state break on every refactor. Testing Library's core philosophy is to test only what the user actually does. Here's why getByRole is the best default, what separates userEvent from fireEvent, and the most common anti-patterns to avoid.

Users found the broken signup before I did after a late-night deploy. How I set up Playwright E2E tests and integrated them into CI to prevent this.

Unit tests all green, but QA finds a bug in three clicks. That's the E2E gap. Here's everything you need to automate real browser scenarios with Playwright — from first test to CI integration.

Frontend development blocked by unfinished APIs. MSW intercepts requests at the network level so you can build and test without a real backend.

My trial-and-error journey introducing frontend testing. Practical patterns for testing React components with Vitest and Testing Library.

Spent a whole night debugging because I confused vi.mock() and vi.spyOn(). Here's a practical deep dive into Vitest's advanced features — mocking strategies, snapshot testing, and why your coverage numbers might be lying to you.

I achieved 100% test coverage, but production crashed immediately. The culprit? Overusing 'fake objects'. I share my failure story caused by confusing Mocks, Stubs, and Spies, and explain the correct way to use Test Doubles.

I was once obsessed with reaching 100% test coverage. After lighting up every line green, I deployed with confidence, only to face a critical bug. I discuss what coverage doesn't tell you, the dangers of meaningless tests, and the true metric of test quality.

Unit tests check the bricks; E2E tests check the building. Learn how to simulate real user journeys using modern tools like Cypress and Playwright. We cover best practices for writing resilient selectors, handling authentication, fighting test flakiness, and where E2E fits in the Testing Pyramid.