How can I mark tests as not having been implemented yet?

describe('the writing of all of these tests is pending', () => {
  it('is the 1st pending test')
  it('is the 2nd pending test', () => {
    expect(2).toBe(2)
    pending()
  })
  xit('is the 3rd pending test', () => {
    expect(3).toBe(3)  
  })
})