I have a problem that I don't know how to solve, I get this error when running npm test

Invariant Violation: You should not use <Switch> outside a <Router>

What can the problem be and how can I solve it? The test I run is the standard app.test.js that comes with react

class App extends Component {

  render() {

    return (

      <div className = 'app'>

        <nav>

          <ul>

            <li><Link exact activeClassName=current to='/'>Home</Link></li>

            <li><Link exact activeClassName=current to='/TicTacToe'>TicTacToe</Link></li>

            <li><Link exact activeClassName=current to='/NumGame'>Quick Maths</Link></li>

            <li><Link exact activeClassName=current to='/HighScore'>Highscore</Link></li>

            <li><Link exact activeClassName=current to='/Profile'>Profile</Link></li>

            <li><Link exact activeClassName=current to='/Login'>Sign out</Link></li>

          </ul>

        </nav>

        <Switch>

          <Route exact path='/' component={Home}></Route>

          <Route path='/TicTacToe' component={TicTacToe}></Route>

          <Route path='/NumGame' component={NumberGame}></Route>

          <Route path='/HighScore' component={HighScore}></Route>

          <Route path='/Profile' component={Profile}></Route>

          <Route path='/Login' component={SignOut1}></Route>

        </Switch>

      </div>

    );

  }

};