Vitest Mocking: Isolating Code with `vi.mock`
Vitest's `vi.mock` replaces a module with a fake version, isolating your code for tests. This is key for preventing real network or database calls. The footgun: calls are "hoisted" to the top of the file, running before other code and breaking variable access.
Vitest's `vi.mock` replaces a real module with a fake one, isolating the code under test. Think of it as swapping a live API client for a dummy that returns predictable data. This is essential for unit testing without real network calls or database writes. The main footgun is hoisting: `vi.mock` is moved to the top of your file before imports, so you can't use variables defined in the test scope inside your mock factory.
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