test("basic functionality", () => {
  expect(isNaN).toHaveLength(1);

  expect(isNaN(0)).toBeFalse();
  expect(isNaN(42)).toBeFalse();
  expect(isNaN("")).toBeFalse();
  expect(isNaN("0")).toBeFalse();
  expect(isNaN("42")).toBeFalse();
  expect(isNaN(true)).toBeFalse();
  expect(isNaN(false)).toBeFalse();
  expect(isNaN(null)).toBeFalse();
  expect(isNaN([])).toBeFalse();
  expect(isNaN(Infinity)).toBeFalse();
  expect(isNaN(-Infinity)).toBeFalse();

  expect(isNaN()).toBeTrue();
  expect(isNaN(NaN)).toBeTrue();
  expect(isNaN(undefined)).toBeTrue();
  expect(isNaN("foo")).toBeTrue();
  expect(isNaN({})).toBeTrue();
  expect(isNaN([1, 2, 3])).toBeTrue();
});