jest.mock example

[nponeccop]

Now that the upstream Jest has some ESM support, there is slightly less need in the esm transform. But their current level of support in jest@next doesn't allow for mocking certain module types.

Can you add some jest.mock examples?

• mocking fs using memfs (built-in modules + nontrivial factory)
• and/or mocking axios requests ("normal" NPM modules)
• snappy or other module with native components