Mocking Imports and Modules.md

[!warning] A Work on Module Systems vi.mock works only for modules that were imported with the import keyword. It doesn't work with require.

Vitest provides vi.mock, which allows you to mock any import that you provide a path for. It's go the following signature:

(path: string, factory?: () => unknown) => void

The factory is a function that you provide as a substitute for whatever really resides at the file path. You'll that it's optional. Here is how it goes down:

1. If you provided a factory function, it will use the return value of that function as the replacement for whatever module lives at path.
2. If you don't provide a factory, but you do have a __mocks__ directory at the same location and an alternative file in that __mocks__ directory, then it will substiture that in.
3. Vitest will use it's automocking algorithm.

Automocking Algorithm

If you don't provide a factory, Vitest will employ its automocking algorithm:

• All arrays will be emptied.
• All primitives and collections will stay the same.
• All objects will be deeply cloned.
• All instances of classes and their prototypes will be deeply cloned.

[!todo] Explain the automocking algorithm You'll probably want to add some kind of visual as well as an example in code and some tests that prove your assumptions.

vi.doMock

vi.doMock is basically the same as vi.mock except for the fact that it's not hoisted to the top, which means you have access to variables. The next import of that module will be mocked.

[!todo] Explain vi.mock hoisting Show with some concrete examples the difference between vi.mock and vi.doMock.