Wrapper is not defined

i'm trying to test one of my react components ReferenceError: wrapper is not defined

 describe('TodaysHabits', () => {
  let component;
  beforeEach(() => {
    wrapper = shallow(<TodayHabits />);
});
 test('it exists', () => {
    expect(wrapper).toExist;
});
test('it contains an p tag', () => {
    const p = wrapper.find('p');
    expect(p.text()).toBe('this is display habits');
 });

});

index.js

import React from 'react';
import moment from 'moment';
import './todayhabits.css';

 class TodayHabits extends React.Component {
   // This component will show the habits that the user has to complete this specific day
   // To do this we need to make a api call to get all habits where they have the respective day as true in the sql
   state = {
       dailyHabits: [],
  }

//for each habit, it will display a new habit component
//we need to pass a prop to each habit component containing that habit's id and title

   displayHabits () {
      return <p>this is display habits</p>

  }

  render() {
      return (
          <div id='dailyHabits'>
              { moment().format('dddd') }, <br/>
              { moment().format("Do MMMM YYYY") } <br/> 
              {this.displayHabits()}
               <button onClick={() => { history.push(`/newHabit`) }}>Add a habit!</button>
        </div>
       )
   }

}

export default TodayHabits;

The errors i'm receiving is that "wrapper is not defined" I tried doing more research on fixing this error but wasn't successfully.