The real reason developers struggle with automated testing is that they rely on rote memorization of framework APIs. Mocks that don’t take effect, Promises or async that won’t resolve with fake timers, mocks leaking into the next test—these problems stem from exactly the same misunderstanding of mechanisms in both `pytest` and `Vitest`. Conversely, once you grasp those mechanisms, you’ll be able to diagnose the cause the moment you see an error message, regardless of the language.
This course consists of 100 hands-on exercises: 50 for pytest (Python) and 50 for Vitest (TypeScript). These two sets of 50 are not a random collection. They follow the same roadmap in parallel across two languages: “first assert → equality and exceptions → parametrize/each → fixtures → mock three-layer reset → async and fake timers → files and in-memory SQLite → HTTP API (FastAPI / Hono) → snapshots → coverage thresholds, TDD, and pseudo-CI.” A concept you understand in one language instantly clicks as a “dialect” in the other—this back-and-forth cultivates a “test design ability” that memorization alone can never achieve.
You can start from either side. Python developers can begin with the pytest track and discover “So this is how JavaScript mocks work” in the Vitest track. Frontend/Node.js developers can start with the Vitest track and confirm “The fixture design philosophy is the same” in the pytest track. By the time you’ve completed both, you’re no longer just a user of a specific framework—you’ve become someone who understands the discipline of testing itself.
