Mocking ES6 instance methods with jest

mockingES6InstanceMethodsWithJest.js

// MyClass/index.js
export class MyClass {
  foo() { /* do something */ }
}

// DependentClass/index.js
import { MyClass } from "../MyClass"
export class DependentClass {
  bar() {
    const foo = new MyClass().foo()
    // do something
  }
}

// DependentClass/tests/index.test.js
import { MyClass } from "../../MyClass"
jest.mock("../../MyClass")

const mockFoo = jest.fn()
MyClass.mockImplementation(() => {
  return { foo: mockFoo }
})

describe("when foo returns false", () => {
  beforeEach(() => {
    mockFoo.mockReturnValue(false)
  })
  
  it("does something", () => {
    // assertions
  })
})