Just how you will test your widget with some tweets depends on how you are managing your class stream:
Hashtag. If you configured your widget to search for a hashtag, then just compose a tweet that contains your hashtag. You should see it show up in the widget!
Likes. If you configured your widget to display the liked tweets from your account, just compose a tweet and then like your own tweet (which seems kind of weird, but it works), and you should see that newly liked tweet show up in your widget.
Class Account. If you have a separate class account, make sure you are logged into that account and then compose a tweet. Any tweet from this account will show up in the widget!
NEXT STEP => And now that you have tweeted, it's time to try another test: retweet and watch how retweets appear in your widget.