mock any browser event

test.spec.js

// example for "scroll"
const simulateEvent = (eventType, e) => {
  const listeners = window.addEventListener.mock.calls.filter((call) => call[0] === eventType).map((call) => call[1])
  listeners.forEach((listener) => listener(e))
}

beforeEach(() => {
  jest.spyOn(window, "addEventListener").mockImplementation(noop)
  jest.spyOn(window, "removeEventListener").mockImplementation(noop)
})

it("passes hidden=true on scroll", () => {
  wrapper = mountComponent(WrapperComponent, props)
  simulateEvent("scroll")
  wrapper.update()

  expect(wrapper.find("ChildComponent").props().hidden).toEqual(true)
})

 // adding/removing the handlers
describe("componentDidMount", () => {
  beforeEach(() => {
    wrapper = mountComponent(WrapperComponent, props)
  })

  it("adds a scroll listener for handleWindowScroll", () => {
    jest.spyOn(window, "addEventListener")
    wrapper.instance().componentDidMount()

    expect(window.addEventListener).toHaveBeenCalledWith("scroll", wrapper.instance().handleWindowScroll)
  })
})

describe("componentWillUnmount", () => {
  it("removes the scroll listener", () => {
    jest.spyOn(window, "removeEventListener")
    wrapper.instance().componentWillUnmount()

    expect(window.removeEventListener).toHaveBeenCalledWith("scroll", wrapper.instance().handleWindowScroll)
  })
})