Header.test.tsx

import "@testing-library/jest-dom";

import { act } from "react";
import { render } from "@testing-library/react";
import { axe, toHaveNoViolations } from "jest-axe";

import Header from "./Header";

jest.mock("next/router", () => ({
  useRouter: jest.fn(() => ({
    events: {
      on: jest.fn(),
    },
  })),
}));

beforeAll(() => {
  expect.extend(toHaveNoViolations);
});

it("Passes accessibility", async () =>
  act(async () => {
    const { container } = render(<Header />);

    const results = await axe(container);

    expect(results).toHaveNoViolations();
  }));