Jest mocks snippets

mocks.tsx

// Mock default constructor
import SomeConstructor from "some-package"

const SomePackageMock = {
    default: jest.fn(),
}
jest.mock("some-package", () => SomePackageMock)

// Import place where construcor from some-package is used
import { testStuff } from "../Scroll/useElementSize"

test("stuff", () => {
    SomePackageMock.default.mockImplementationOnce(function(): any {
      // here mocked implementation goes
    })
})