jest-mock-proxy

[![buid][ci-badge]][ci] [![buid][coverage-badge]][coverage] [![version][version-badge]][package] [![MIT License][license-badge]][license]

> Mock classes and objects with the power of proxies!

Creates a Proxy that will dynamically create spies when a property is accessed the first time.
Every subsequent access will use the same spy. In combination with TypeScript this allows us to create a mock for any class/object without having to specify all its properties and methods.

tl;dr;

1. The Proxy makes any property and method available on the mock at runtime.
2. TypeScript limits access to properties and methods to the specified generic.

Install

_Requires node 8+._

``
$ yarn add -D jest-mock-proxy
`

or

`
$ npm install -D jest-mock-proxy
`

Usage

$3

`ts
// service.ts
export class Service {
foo() {
console.log('hello');
}
bar(s: string) {
return s;
}
}

// some.test.ts
import { createMockProxy } from 'jest-mock-proxy';
import { service } from './service';

const mock = createMockProxy();

mock.foo();

mock.bar.mockReturnValue('some string');
mock.bar('test'); // 'some string'
`

#### Example: Mock an elastic search client.

`ts
import { Client } from 'elasticsearch';
import { createMockProxy } from 'jest-mock-proxy';
import fixture from './__fixtures__/elastic-response.json';

// This is an imaginary service that depends on the elastic search client.
import createService from './createService';

const client = createMockProxy();
const service = createService(client);

beforeEach(() => {
client.mockClear();
client.search.mockResolvedValue(fixture);
});

test('use service to query', async () => {
await service.query('https://example.com?q=hello');
expect(client.search.mock.calls).toMatchSnapshot();
});
`

$3

When you need to mock a dependency via jest.mock, because you have no access to the module.

`ts
// query.ts
import { Pool, PoolConfig } from 'pg';

// 😨 This makes testing hard...
const pool = new Pool();

export const query = async (q: string, values?: any[]) => {
// ...because how to mock this?
const { rows } = pool.query(q, values);
return rows;
};

// query.test.ts
import { Pool } from 'pg';
import { createProxyFromMock } from 'jest-mock-proxy';

import { query } from './query';

jest.mock('pg');
const mockedPool = createProxyFromMock(Pool);

test('you can now mock the pool.query', async () => {
// Use mockedPool so you get good type inference from TS
mockedPool.query.mockResolvedValue({ rows: [{ id: 1, data: 'data' }] });

await query('SELECT * FROM table1'); // returns [{ id: 1, data: 'data' }]
});
``

[ci]: https://actions-badge.atrox.dev/sebald/jest-mock-proxy/goto?ref=master
[ci-badge]: https://img.shields.io/endpoint.svg?url=https%3A%2F%2Factions-badge.atrox.dev%2Fsebald%2Fjest-mock-proxy%2Fbadge%3Fref%3Dmaster&style=flat-square
[coverage]: https://codecov.io/gh/sebald/jest-mock-proxy
[coverage-badge]: https://img.shields.io/codecov/c/github/sebald/jest-mock-proxy.svg?style=flat-square
[license]: https://github.com/sebald/jest-mock-proxy/blob/master/LICENCE
[license-badge]: https://img.shields.io/npm/l/jest-mock-proxy.svg?style=flat-square
[package]: https://www.npmjs.com/package/jest-mock-proxy
[version-badge]: https://img.shields.io/npm/v/jest-mock-proxy.svg?style=flat-square