experiment: mock objects generation.

[vidup]

This PR adds a new feature: returning/resolving values corresponding to validation and anyXXX matchers instead of specific values. The objective is:

• to speed-up writing tests with categories of values (which matchers are).
• to accept zod schemas, which can help mock APIs thanks to their related validation schemas.

It works like this:

For matchers of anyXXX format, you can pass them in thenReturn/thenResolve, and it will generate a value that would pass this matcher in assertions.

const mock = m.Mock(hi);
m.when(mock).isCalled.thenReturn(m.anyArray());

mock(); // an array

For zod schemas, you can pass them as well in their dedicated matcher (m.validates). To make this works you will need to install two dependencies:

npm install zod @faker-js/faker @anatine/zod-mock

zod-mock is a package that will generate a valid value for a given zod schema. It requires faker (hence the second dependency).
These dependencies are peerDependencies of Mockit: this specific feature won't work if you didn't create it.

test("thenReturn should accept a Zod schema and return a valid object", () => {
    // In a real world scenario, you will import this schema from the module under test.
    const schema = z.object({
        name: z.string(),
        age: z.number(),
    });
    
    const mock = m.Mock(hi)
    m.when(mock).isCalled.thenReturn(m.validates(schema));
    
    const result = mock();
    expect(result).toMatchObject({
        name: expect.any(String),
        age: expect.any(Number),
    })
});

Thoughs

Honestly I'm not sure if this is really useful, considering the fact that people could just install zod-mock (which they will need to do since I'm not planning on bundling it with Mockit), and could then just call thenReturn(generateMock(schema)).

Todo

• Make it work on thenResolve
• remove coupling between anyXXX matchers and zod-mock.
• decide if this is actually a useful addition.