natural_DI.js

// factoryA.js
import FactoryB from './factoryB'

export default class FactoryA {
	constructor(data) {
		// ...
	}
	
	doStuffWithB(data, B = FactoryB) {
		const b = new B()
		return b.foo(data)
	}
}

// factoryA.test.js
describe('FactoryA', () => {
	it('doStuffWithB', () => {
		const mockData = ['foo']
		const a = new FactoryA()
		const foo = jest.fn(() => 'test')
		const MockFactoryB = jest.fn(() => ({foo}))
		expect(a.doStuffWithB(mockData, MockFactoryB)).toBe('test')
		expect(foo).toBeCalledWith(mockData)
	})
})